First of all, sorry if this has been reported already, but there are so many posts on this forum, I just search a few minutes, i confess...
I've noticed an issue: changing a cover îmage by a lighter one doesn't decrease the file length. In fact, on a FLAC file, i had a 2 MB picture that I changed by a 300 Kb one, but the file size stays the same.
I tried adding multiple pictures to get a very big FLAC file (45 MB with only 15 MB of audio, the rest in covers), then removing all the covers... the file was still 45 MB.
I've changed huge pictures by smaller ones on so many files... for nothing
Apart from that, well there's not much to say, it's an amazing software