I sometimes do mistakes. I press CTRL-R although I still haven't saved metadata in another tag.
One typical example: I have some MP3 tracks, they have ID3v1 & ID3v2.2 tags which I want to convert to APEv2.
My default settings are Read ID3v1, ID3v2, APE - Write APEv2 - Remove ID3v1, ID3v2.
So I have the MP3s loaded up in Mp3Tag but mistakenly press CTRL-R instead of CTRL-S, I immidiately cancel the action, which usually saves the ID3v2 tags and only leaves me with some ID3v1 being deleted as they are removed first and the v2 tags last.
But it also happen that I don't cancel it and then it's too late. The tags are gone.
Now in either case, when I do "Undo Remove tag" the ID3v1/2 tags do not get written back to the mp3s! But when it was APEv2 tags I deleted then they are recovered!
Is this intended behaviour?