I've requested example files and they contain various unsupported GEOB and PRIV ID3v2 frames. It's likely that the DAP chokes on those, as they can appear in a different order on rewrites.
Removing the tag of those files via Edit → Remove Tag[1] and undoing the change via Edit → Undo removes those unsupported frames, so that the file might appear to be "repaired".
You can display those unsupported frames by adding a new column to the File List using %_id3v2_unknown_frames% as Value. A filter with NOT %_id3v2_unknown_frames% IS "" lists all files with unsupported frames.
Removing ID3v2 at Settings → Tag Types → Remove needs to be enabled for this workaround to be effective. ↩︎