It seems like the DICOMGDCMTagScanner is not working correctly (DICOMDatasetFinding::path is not set, leading to wrong property names).
Thus all current DICOMReader classes in default configuration does not work. If you use DICOMDCMTKTagScanner with the reader (like in the reader services) everythin works fine.
This was also a problem for the error reported in T22840.