This is a bug that was introduced in v2.45a (it was not in any previous version I've used 2.44*).
- Load a largish list of songs (I'm doing it with 6000, but a few dozen would likely work too).
- Enable the filter field (F3).
- Type a filter that reduces the list of songs down to about 10 (the exact number doesn't seem to matter, but it can't be too small ... I can't seem to reproduce this below about 4).
- Select 2 or more of the songs (not the first, not the last).
- Hit CTRL+DELETE.
After the songs have been deleted, some of the songs that were NOT deleted have changed into songs that were not in the original list of filtered songs.
I can reproduce this almost every time I try, but occasionally it seems to work ok.
I does appear that mp3tag is deleting the correct songs and if I change the filter field, it immediately corrects the contents of the list.