Found a console crashing bug that makes the song editor open pattern -1. For me so far it's only displayed track 00, hasn't been able to play, and if I try to save while -1 is open, PICO-8 crashes and doesn't save.
I've repeated it a couple of times but still don't have a concrete way of getting -1. The time I remember most of what I did when it occured was when I had 6 tracks of a song (00-06, speed was 22, tracks were in channels 1,2 and 3 in the song editor), one track for the test (08, speed may have been 22 or 16, it was in channel 4), and I played the song from pattern 00 (it ends in pattern 02) twice. Once I held down a note while the song was playing to fill track 8, and the second time I held down a different note till it filled track 8. As soon as the song ended (I held down the second note till the end) the song editor opened pattern -1 which had track 00 for all its channels, all 4 of which enabled. Ctrl+S resulted in a crash and no save.

I forgot there were buttons for record and screenshot. Pics of display attached :P