Can't Add Custom Album Art to FLAC

[ohrenkino]

See e.g. here:

Audacity-created FLAC files corrupt when adding cover

I am ripping some LPs to my library. For several reasons I keep each files in BOTH MP3 and FLAC forms. I have had no other issues with using MP3Tag to add cover art to flac files. It is often able to do this when other software can't. However, with this set of files when I add cover art in MP3 Tag (no other thing done) it immediately corrupts the file. Like: file will play in MP3Tag, add cover art (&save) file won't play. You can see in windows explorer as all of the metadata disappears th…