Cannot tag MP4 files converted from DVD (VOB) to MP4

Cannot tag MP4 files converted from DVD (VOB) to MP4:

I am using Wonder share Video Converter to convert different video formats to MP4. No problems with the exception of files converted from old ripped DVD's.

I am unable to tag these VOB-MP4 files. I enter the data but MP3tag does not save the data. If I use itunes or TagRename I am able to create MP4 tags. However this tag data does not show in Mp3Tag

Any Ideas?

Use a different video converter? Just as a test?

I have the same problem after ffmpeg.
sometimes it works just fine and I can read/edit mp4 tags
sometimes whenever I change and save tags they disappear from mp3tag and explorer properties
I tried tagscan to edit tags and ended up with tagscan/explorer showing one value (i.e. for title) and mp3tag another

changing tools/options/tags seems to have no effect on mp4 tags