I've recently discovered while trying to retag some files that foo_playcount adds play count information as APEv2. (Or so dBpowerAmp tells me.) I then edit the tags without problems, but the tag information keeps returning to what it was after I play it in foobar. This is irritating as I spent ages trying to work out why it has APEv2 tags before I realised it was actually foo_playcount that is doing this.

I have now removed foo_playcount, but files that has playcount information still can't be edited without removing the APEv2 tags. Is there any way to quick remove the tags without erasing ID3v2/FLAC tags?

Seems like foobar is showing/re-writing the tags from it's database after you edit the tags of files in an external program. Try nuking the foobar database, restart foobar, and scan tracks again.