diff --git a/Modules/DICOM/src/mitkDICOMTagBasedSorter.cpp b/Modules/DICOM/src/mitkDICOMTagBasedSorter.cpp
index 7c8977956b..af65bb55da 100644
--- a/Modules/DICOM/src/mitkDICOMTagBasedSorter.cpp
+++ b/Modules/DICOM/src/mitkDICOMTagBasedSorter.cpp
@@ -1,633 +1,634 @@
 /*============================================================================
 
 The Medical Imaging Interaction Toolkit (MITK)
 
 Copyright (c) German Cancer Research Center (DKFZ)
 All rights reserved.
 
 Use of this source code is governed by a 3-clause BSD license that can be
 found in the LICENSE file.
 
 ============================================================================*/
 
 #include "mitkDICOMTagBasedSorter.h"
 
 #include <algorithm>
 #include <iomanip>
 
 mitk::DICOMTagBasedSorter::CutDecimalPlaces
 ::CutDecimalPlaces(unsigned int precision)
 :m_Precision(precision)
 {
 }
 
 mitk::DICOMTagBasedSorter::CutDecimalPlaces
 ::CutDecimalPlaces(const CutDecimalPlaces& other)
 :m_Precision(other.m_Precision)
 {
 }
 
 std::string
 mitk::DICOMTagBasedSorter::CutDecimalPlaces
 ::operator()(const std::string& input) const
 {
   // be a bit tolerant for tags such as image orientation orientation, let only the first few digits matter (https://phabricator.mitk.org/T12263)
   // iterate all fields, convert each to a number, cut this number as configured, then return a concatenated string with all cut-off numbers
   std::ostringstream resultString;
   resultString.str(std::string());
   resultString.clear();
   resultString.setf(std::ios::fixed, std::ios::floatfield);
   resultString.precision(m_Precision);
 
   std::stringstream ss(input);
   ss.str(input);
   ss.clear();
   std::string item;
   double number(0);
   std::istringstream converter(item);
   while (std::getline(ss, item, '\\'))
   {
     converter.str(item);
     converter.clear();
     if (converter >> number && converter.eof())
     {
       // converted to double
       resultString << number;
     }
     else
     {
       // did not convert to double
       resultString << item; // just paste the unmodified string
     }
 
     if (!ss.eof())
     {
       resultString << "\\";
     }
   }
 
   return resultString.str();
 }
 
 mitk::DICOMTagBasedSorter::TagValueProcessor*
 mitk::DICOMTagBasedSorter::CutDecimalPlaces
 ::Clone() const
 {
   return new CutDecimalPlaces(*this);
 }
 
 
 unsigned int
 mitk::DICOMTagBasedSorter::CutDecimalPlaces
 ::GetPrecision() const
 {
   return m_Precision;
 }
 
 mitk::DICOMTagBasedSorter
 ::DICOMTagBasedSorter()
 :DICOMDatasetSorter()
 ,m_StrictSorting(m_DefaultStrictSorting)
 ,m_ExpectDistanceOne(m_DefaultExpectDistanceOne)
 {
 }
 
 mitk::DICOMTagBasedSorter
 ::~DICOMTagBasedSorter()
 {
   for(auto ti = m_TagValueProcessor.cbegin();
       ti != m_TagValueProcessor.cend();
       ++ti)
   {
     delete ti->second;
   }
 }
 
 mitk::DICOMTagBasedSorter
 ::DICOMTagBasedSorter(const DICOMTagBasedSorter& other )
 :DICOMDatasetSorter(other)
 ,m_DistinguishingTags( other.m_DistinguishingTags )
 ,m_SortCriterion( other.m_SortCriterion )
 ,m_StrictSorting( other.m_StrictSorting )
 ,m_ExpectDistanceOne( other.m_ExpectDistanceOne )
 {
   for(auto ti = other.m_TagValueProcessor.cbegin();
       ti != other.m_TagValueProcessor.cend();
       ++ti)
   {
     m_TagValueProcessor[ti->first] = ti->second->Clone();
   }
 }
 
 mitk::DICOMTagBasedSorter&
 mitk::DICOMTagBasedSorter
 ::operator=(const DICOMTagBasedSorter& other)
 {
   if (this != &other)
   {
     DICOMDatasetSorter::operator=(other);
     m_DistinguishingTags = other.m_DistinguishingTags;
     m_SortCriterion = other.m_SortCriterion;
     m_StrictSorting = other.m_StrictSorting;
     m_ExpectDistanceOne = other.m_ExpectDistanceOne;
 
     for(auto ti = other.m_TagValueProcessor.cbegin();
         ti != other.m_TagValueProcessor.cend();
         ++ti)
     {
       m_TagValueProcessor[ti->first] = ti->second->Clone();
     }
   }
   return *this;
 }
 
 bool
 mitk::DICOMTagBasedSorter
 ::operator==(const DICOMDatasetSorter& other) const
 {
   if (const auto* otherSelf = dynamic_cast<const DICOMTagBasedSorter*>(&other))
   {
     if (this->m_StrictSorting != otherSelf->m_StrictSorting) return false;
     if (this->m_ExpectDistanceOne != otherSelf->m_ExpectDistanceOne) return false;
 
     bool allTagsPresentAndEqual(true);
     if (this->m_DistinguishingTags.size() != otherSelf->m_DistinguishingTags.size())
       return false;
 
     for (auto myTag = this->m_DistinguishingTags.cbegin();
         myTag != this->m_DistinguishingTags.cend();
         ++myTag)
     {
       allTagsPresentAndEqual &= (std::find( otherSelf->m_DistinguishingTags.cbegin(), otherSelf->m_DistinguishingTags.cend(), *myTag )
                                  != otherSelf->m_DistinguishingTags.cend()); // other contains this tags
                                              // since size is equal, we don't need to check the inverse
     }
 
     if (!allTagsPresentAndEqual) return false;
 
     if (this->m_SortCriterion.IsNotNull() && otherSelf->m_SortCriterion.IsNotNull())
     {
       return *(this->m_SortCriterion) == *(otherSelf->m_SortCriterion);
     }
     else
     {
       return this->m_SortCriterion.IsNull() && otherSelf->m_SortCriterion.IsNull();
     }
   }
   else
   {
     return false;
   }
 }
 
 void
 mitk::DICOMTagBasedSorter
 ::PrintConfiguration(std::ostream& os, const std::string& indent) const
 {
   os << indent << "Tag based sorting "
      << "(strict=" << (m_StrictSorting?"true":"false")
      << ", expectDistanceOne=" << (m_ExpectDistanceOne?"true":"false") << "):"
      << std::endl;
 
   for (auto tagIter = m_DistinguishingTags.begin();
        tagIter != m_DistinguishingTags.end();
        ++tagIter)
   {
     os << indent << "  Split on ";
     tagIter->Print(os);
     os << std::endl;
   }
 
   DICOMSortCriterion::ConstPointer crit = m_SortCriterion.GetPointer();
   while (crit.IsNotNull())
   {
     os << indent << "   Sort by ";
     crit->Print(os);
     os << std::endl;
     crit = crit->GetSecondaryCriterion();
   }
 }
 
 void
 mitk::DICOMTagBasedSorter
 ::SetStrictSorting(bool strict)
 {
   m_StrictSorting = strict;
 }
 
 bool
 mitk::DICOMTagBasedSorter
 ::GetStrictSorting() const
 {
   return m_StrictSorting;
 }
 
 void
 mitk::DICOMTagBasedSorter
 ::SetExpectDistanceOne(bool strict)
 {
   m_ExpectDistanceOne = strict;
 }
 
 bool
 mitk::DICOMTagBasedSorter
 ::GetExpectDistanceOne() const
 {
   return m_ExpectDistanceOne;
 }
 
 
 mitk::DICOMTagList
 mitk::DICOMTagBasedSorter
 ::GetTagsOfInterest()
 {
   DICOMTagList allTags = m_DistinguishingTags;
 
   if (m_SortCriterion.IsNotNull())
   {
     const DICOMTagList sortingRelevantTags = m_SortCriterion->GetAllTagsOfInterest();
     allTags.insert( allTags.end(), sortingRelevantTags.cbegin(), sortingRelevantTags.cend() ); // append
   }
 
   return allTags;
 }
 
 mitk::DICOMTagList
 mitk::DICOMTagBasedSorter
 ::GetDistinguishingTags() const
 {
   return m_DistinguishingTags;
 }
 
 const mitk::DICOMTagBasedSorter::TagValueProcessor*
 mitk::DICOMTagBasedSorter
 ::GetTagValueProcessorForDistinguishingTag(const DICOMTag& tag) const
 {
   auto loc = m_TagValueProcessor.find(tag);
   if (loc != m_TagValueProcessor.cend())
   {
     return loc->second;
   }
   else
   {
     return nullptr;
   }
 }
 
 void
 mitk::DICOMTagBasedSorter
 ::AddDistinguishingTag( const DICOMTag& tag, TagValueProcessor* tagValueProcessor )
 {
   m_DistinguishingTags.push_back(tag);
   m_TagValueProcessor[tag] = tagValueProcessor;
 }
 
 void
 mitk::DICOMTagBasedSorter
 ::SetSortCriterion( DICOMSortCriterion::ConstPointer criterion )
 {
   m_SortCriterion = criterion;
 }
 
 mitk::DICOMSortCriterion::ConstPointer
 mitk::DICOMTagBasedSorter
 ::GetSortCriterion() const
 {
   return m_SortCriterion;
 }
 
 void
 mitk::DICOMTagBasedSorter
 ::Sort()
 {
   SplitReasonListType splitReasons;
 
   // 1. split
   GroupIDToListType groups = this->SplitInputGroups(splitReasons);
 
   // 2. sort each group (can also lead to a split due to distance)
   GroupIDToListType& sortedGroups = this->SortGroups( groups, splitReasons);
 
   // 3. define output
   this->SetNumberOfOutputs(sortedGroups.size());
   unsigned int outputIndex(0);
   for (auto groupIter = sortedGroups.cbegin();
        groupIter != sortedGroups.cend();
        ++outputIndex, ++groupIter)
   {
     this->SetOutput(outputIndex, groupIter->second, splitReasons[groupIter->first]);
   }
 }
 
 std::string
 mitk::DICOMTagBasedSorter
 ::BuildGroupID( DICOMDatasetAccess* dataset )
 {
   // just concatenate all tag values
   assert(dataset);
   std::stringstream groupID;
   groupID << "g";
   for (auto tagIter = m_DistinguishingTags.cbegin();
        tagIter != m_DistinguishingTags.cend();
        ++tagIter)
   {
     groupID << tagIter->GetGroup() << tagIter->GetElement(); // make group/element part of the id to cover empty tags
     DICOMDatasetFinding rawTagValue = dataset->GetTagValueAsString(*tagIter);
     std::string processedTagValue;
     if ( m_TagValueProcessor[*tagIter] != nullptr && rawTagValue.isValid)
     {
       processedTagValue = (*m_TagValueProcessor[*tagIter])(rawTagValue.value);
     }
     else
     {
       processedTagValue = rawTagValue.value;
     }
     groupID << "#" << processedTagValue;
   }
   // shorten ID?
   return groupID.str();
 }
 
 mitk::DICOMTagBasedSorter::GroupIDToListType
 mitk::DICOMTagBasedSorter
 ::SplitInputGroups(SplitReasonListType& splitReasons)
 {
   DICOMDatasetList input = GetInput(); // copy
 
   GroupIDToListType listForGroupID;
 
   for (auto dsIter = input.cbegin();
        dsIter != input.cend();
        ++dsIter)
   {
     DICOMDatasetAccess* dataset = *dsIter;
     assert(dataset);
 
     const std::string groupID = this->BuildGroupID( dataset );
     MITK_DEBUG << "Group ID for for " << dataset->GetFilenameIfAvailable() << ": " << groupID;
     listForGroupID[groupID].push_back(dataset);
   }
 
   MITK_DEBUG << "After tag based splitting: " << listForGroupID.size() << " groups";
 
   splitReasons.clear();
   if (listForGroupID.size() == 1)
   {
     //no split -> no reason
     splitReasons[listForGroupID.begin()->first] = IOVolumeSplitReason::New();
   }
   else
   {
     for (auto& [key, value] : listForGroupID)
     {
+      (void)value; // Prevent unused variable error in older compilers
       auto reason = IOVolumeSplitReason::New();
       reason->AddReason(IOVolumeSplitReason::ReasonType::ValueSplitDifference);
       splitReasons[key] = reason;
     }
   }
 
   return listForGroupID;
 }
 
 mitk::DICOMTagBasedSorter::GroupIDToListType&
 mitk::DICOMTagBasedSorter
 ::SortGroups(GroupIDToListType& groups, SplitReasonListType& splitReasons)
 {
   if (m_SortCriterion.IsNotNull())
   {
     /*
        Three steps here:
         1. sort within each group
            - this may result in orders such as 1 2 3 4 6 7 8 10 12 13 14
         2. create new groups by enforcing consecutive order within each group
            - resorts above example like 1 2 3 4  ;  6 7 8  ;  10  ;  12 13 14
         3. sort all of the groups (not WITHIN each group) by their first frame
            - if earlier "distinguish" steps created groups like 6 7 8  ;  1 2 3 4  ; 10,
              then this step would sort them like 1 2 3 4  ;  6 7 8  ;  10
     */
 
     // Step 1: sort within the groups
     // for each output
     //   sort by all configured tags, use secondary tags when equal or empty
     //   make configurable:
     //    - sorting order (ascending, descending)
     //    - sort numerically
     //    - ... ?
 #ifdef MBILOG_ENABLE_DEBUG
     unsigned int groupIndex(0);
 #endif
     for (auto gIter = groups.begin();
          gIter != groups.end();
 #ifdef MBILOG_ENABLE_DEBUG
          ++groupIndex,
 #endif
          ++gIter)
     {
       DICOMDatasetList& dsList = gIter->second;
 
 #ifdef MBILOG_ENABLE_DEBUG
       MITK_DEBUG << "   --------------------------------------------------------------------------------";
       MITK_DEBUG << "   DICOMTagBasedSorter before sorting group : " << groupIndex;
       for (auto oi = dsList.begin();
            oi != dsList.cend();
            ++oi)
       {
         MITK_DEBUG << "     INPUT     : " << (*oi)->GetFilenameIfAvailable();
       }
 #endif // #ifdef MBILOG_ENABLE_DEBUG
 
 
       std::sort( dsList.begin(), dsList.end(), ParameterizedDatasetSort( m_SortCriterion ) );
 
 #ifdef MBILOG_ENABLE_DEBUG
       MITK_DEBUG << "   --------------------------------------------------------------------------------";
       MITK_DEBUG << "   DICOMTagBasedSorter after sorting group : " << groupIndex;
       for (auto oi = dsList.cbegin();
            oi != dsList.cend();
            ++oi)
       {
         MITK_DEBUG << "     OUTPUT    : " << (*oi)->GetFilenameIfAvailable();
       }
       MITK_DEBUG << "   --------------------------------------------------------------------------------";
 
 #endif // MBILOG_ENABLE_DEBUG
 
     }
 
     GroupIDToListType consecutiveGroups;
     SplitReasonListType consecutiveReasons;
     if (m_StrictSorting)
     {
       // Step 2: create new groups by enforcing consecutive order within each group
       unsigned int groupIndex(0);
       for (auto gIter = groups.begin();
            gIter != groups.end();
            ++gIter)
       {
         std::stringstream groupKey;
         groupKey << std::setfill('0') << std::setw(6) << groupIndex++;
         std::string groupKeyStr = groupKey.str();
 
         DICOMDatasetList& dsList = gIter->second;
 
         DICOMDatasetAccess* previousDS(nullptr);
         unsigned int dsIndex(0);
         double constantDistance(0.0);
         bool constantDistanceInitialized(false);
         for (auto dataset = dsList.cbegin();
              dataset != dsList.cend();
              ++dsIndex, ++dataset)
         {
           bool splitted = false;
           if (dsIndex >0) // ignore the first dataset, we cannot check any distances yet..
           {
             // for the second and every following dataset:
             // let the sorting criterion calculate a "distance"
             // if the distance is not 1, split off a new group!
             const double currentDistance = m_SortCriterion->NumericDistance(previousDS, *dataset);
             if (constantDistanceInitialized)
             {
               if (fabs(currentDistance - constantDistance) < fabs(constantDistance * 0.01)) // ok, deviation of up to 1% of distance is tolerated
               {
                 // nothing to do, just ok
                 MITK_DEBUG << "Checking currentDistance==" << currentDistance << ": small enough";
               }
               //else if (currentDistance < mitk::eps) // close enough to 0
               else
               {
                 MITK_DEBUG << "Split consecutive group at index " << dsIndex << " (current distance " << currentDistance << ", constant distance " << constantDistance << ")";
                 // split! this is done by simply creating a new group (key)
                 groupKey.str(std::string());
                 groupKey.clear();
                 groupKey << std::setfill('0') << std::setw(6) << groupIndex++;
                 groupKeyStr = groupKey.str();
                 splitted = true;
               }
             }
             else
             {
               // second slice: learn about the expected distance!
 
               // heuristic: if distance is an integer, we check for a special case:
               //            if the distance is integer and not 1/-1, then we assume
               //            a missing slice right after the first slice
               //            ==> split off slices
               // in all other cases: second dataset at this position, no need to split already, we are still learning about the images
 
               // addition to the above: when sorting by imagepositions, a distance other than 1 between the first two slices is
               // not unusual, actually expected... then we should not split
 
               if (m_ExpectDistanceOne)
               {
                 if ((currentDistance - (int)currentDistance == 0.0) && fabs(currentDistance) != 1.0)
                   // exact comparison. An integer should not be expressed as 1.000000000000000000000000001!
                 {
                   MITK_DEBUG << "Split consecutive group at index " << dsIndex << " (special case: expected distance 1 exactly)";
                   groupKey.str(std::string());
                   groupKey.clear();
                   groupKey << std::setfill('0') << std::setw(6) << groupIndex++;
                   groupKeyStr = groupKey.str();
                   splitted = true;
                 }
               }
 
               MITK_DEBUG << "Initialize strict distance to currentDistance=" << currentDistance;
 
               constantDistance = currentDistance;
               constantDistanceInitialized = true;
             }
           }
           consecutiveGroups[groupKeyStr].push_back(*dataset);
 
           if (consecutiveReasons.find(groupKeyStr) == consecutiveReasons.end())
           {
             auto dsReason = splitReasons[gIter->first]->Clone();
             if (splitted)
               dsReason->AddReason(IOVolumeSplitReason::ReasonType::ValueSortDistance);
             consecutiveReasons[groupKeyStr] = dsReason;
           }
 
           previousDS = *dataset;
         }
       }
     }
     else
     {
       consecutiveGroups = groups;
     }
 
     // Step 3: sort all of the groups (not WITHIN each group) by their first frame
     /*
       build a list-1 of datasets with the first dataset one of each group
       sort this list-1
       build a new result list-2:
        - iterate list-1, for each dataset
          - find the group that contains this dataset
          - add this group as the next element to list-2
       return list-2 as the sorted output
     */
     DICOMDatasetList firstSlices;
     for (auto gIter = consecutiveGroups.cbegin();
          gIter != consecutiveGroups.cend();
          ++gIter)
     {
       assert(!gIter->second.empty());
       firstSlices.push_back(gIter->second.front());
     }
 
     std::sort( firstSlices.begin(), firstSlices.end(), ParameterizedDatasetSort( m_SortCriterion ) );
 
     GroupIDToListType sortedResultBlocks;
     SplitReasonListType sortedResultsReasons;
 
     for (auto& [key, group] : consecutiveGroups)
     {
       auto findSliceIterator = std::find(firstSlices.begin(), firstSlices.end(), group.front());
 
       std::stringstream groupKey;
       groupKey << std::setfill('0') << std::setw(6) << std::distance(firstSlices.begin(),findSliceIterator); // try more than 999,999 groups and you are doomed (your application already is)
       const auto groupKeyStr = groupKey.str();
       sortedResultBlocks[groupKeyStr] = group;
       sortedResultsReasons[groupKeyStr] = consecutiveReasons[key];
     }
 
     groups = sortedResultBlocks;
     splitReasons = sortedResultsReasons;
   }
 
 #ifdef MBILOG_ENABLE_DEBUG
   unsigned int groupIndex( 0 );
   for ( auto gIter = groups.begin(); gIter != groups.end(); ++groupIndex, ++gIter )
   {
     DICOMDatasetList& dsList = gIter->second;
     MITK_DEBUG << "   --------------------------------------------------------------------------------";
     MITK_DEBUG << "   DICOMTagBasedSorter after sorting group : " << groupIndex;
     for ( auto oi = dsList.begin(); oi != dsList.end(); ++oi )
     {
       MITK_DEBUG << "     OUTPUT    : " << ( *oi )->GetFilenameIfAvailable();
     }
     MITK_DEBUG << "   --------------------------------------------------------------------------------";
   }
 #endif // MBILOG_ENABLE_DEBUG
 
 
 
   return groups;
 }
 
 mitk::DICOMTagBasedSorter::ParameterizedDatasetSort
 ::ParameterizedDatasetSort(DICOMSortCriterion::ConstPointer criterion)
 :m_SortCriterion(criterion)
 {
 }
 
 bool
 mitk::DICOMTagBasedSorter::ParameterizedDatasetSort
 ::operator() (const mitk::DICOMDatasetAccess* left, const mitk::DICOMDatasetAccess* right)
 {
   assert(left);
   assert(right);
   assert(m_SortCriterion.IsNotNull());
 
   return m_SortCriterion->IsLeftBeforeRight(left, right);
 }