I'm getting an error error reading value unexpected EOF when attempting to parse a DICOM.

After doing a bit of debugging, I determined the problem is occurring because the DICOM has an implicit transfer syntax and a tag that is outside of the DICOM standard (0029,1140 ApplicationHeaderSequence SQ). This is causing the VR to be "UN" and the tag to be read as a string with a length of 4GB, which obviously fails.

Is there a way I can add a custom tag to the DICOM dict so it is correctly identified with a VR of "SQ"? Or is there another way around this problem?

I can upload the DICOM I'm getting this error on later if that will be helpful.