I have multiple autoplaylists where, after a few days, I would look and notice a lot of songs missing. These songs that were removed still met the criteria, so they should have stayed. I know this for sure because I verified the metadata of some of the removed songs.
The biggest proof that something is up (and that thankfully acts as a kind of temporary workaround), is that if I open up the edit screen for the autoplaylist, then save it (don't even need to make any changes), MB rescans my library and puts those removed songs back into the autoplaylist. My most recent encounter with this: The playlist had 2,235 songs in it. I re-save the autoplaylist settings, and the number shoots back up to 2,733 songs. That's a difference of a removal of ~500 songs, in one week!!
Here are the settings for that problematic autoplaylist:
I can't figure this one out for the life of me. My settings for the autoplaylist are basic and fine, so what is causing this? When I am watching it to see if it will remove the song after playing it, it most often does not. And then when I leave it playing in the background it chains one removal after another! They seem to happen in sets until I re-save the playlist settings...
I'd love to know if you have any ideas.