In D250 a change was made to the QmitkAbstractNodeSelectionWidget: https://phabricator.mitk.org/D250#inline-1868 which changed the type signature of the signal being emitted by sub-classes. This leads to undefined signals and thus broken signal-slot connections.
I propose to re-check the refactored plugins and change the connect's from something like this
connect(selectionSlot, SIGNAL(CurrentSelectionChanged(QList<mitk::DataNode::Pointer>)), selectionReceiver, SLOT(ChangeServiceSelection(QList<mitk::DataNode::Pointer>)));
to something like this
connect(selectionSlot, &QmitkAbstractNodeSelectionWidget::CurrentSelectionChanged, selectionReceiver, &QmitkSelectionServiceConnector::ChangeServiceSelection);