To issue a bug report, I think that your post lacks a number of vital pieces of information.
What kind of files do you treat? MP3? Flac? Wav? Mp4?
Have you run the unwilling files through tools that check the integrity like linked here: How to check files for errors?
How do you know that the other tagger has made it better and not worse like e.g. simply stacked further tags on top of already existing but corrupt tags?
Are the files taggable if you move them to a different folder?
And what about other programs that access the files at the same time? have you made sure that there is none running and how did you do that?
And finally: if all these local checks still so not lead to a solution, it would be nice to get a sample file.