I've just tried 0.9.2 beta 4, not sure about the previous 0.9.x series.

if you have 2 playlists (or more, but 2 will be ok), playlist 1, and playlist 2.

playlist 1 contains a lot of songs, but the locations of the songs are wrong (old locations, the files are moved somewhere else)

then, for example, try to play the first song in playlist 1, the error window will pop up, then you close the error window, at this time foobar2000 is still looking for other songs in the list (because the list is big), you remove playlist 1.

since foobar is keeping the item index number of the next song to try, but playlist 1 is removed, the song with the same index number in the next playlist (playlist 2) will be played.

this behavior never happened in 0.8.3, because this old version will only try to play that specific song, and stop looking for other songs.