OK, the difference in slice orientations explain why Slicer shows all those loadables separately. You can disable showing these (just to clean up the view a bit), in Application Settings / DICOM / Allow loading subseries by time.
Then, enable “Acquisition geometry regularization” and try each “DICOM reader approach”.
What software has created these files?
@pieper Does acquisition regularization can fix up series with not-exactly-parallel slices?