I have used MP3Tag for years on Mac (in combination with the Wineskin tool).
At last, a Mac version!
I installed the trial version the day before yesterday, and the conclusion is this:
the Mac version seemed great but messed up my Serato tags!
=> Colour codes: I got some weird colours in Serato, some colours disappeared, other files changed colours.
=> Some files are now unlocked: beatgrids are unlocked, and are no longer correct in most cases
=> Some tags in the comments field have vanished
=> Some files now have new cue markers in weird colours, when I play these files, Serato freezes.
=> Some files got corrupt.
The files were all MP4 music videos.
I used MP3Tag for tag conversion to uppercase.
What did I do wrong?