Sustain completely broken in the GarageBand editor

I just finished composing a track in GarageBand, used sustain for the entire duration.

During editing, I noticed that only the first segment of the track had sustain, joined the segments to try making the sustain fully continuous.

The sustain promptly disappeared, and no I don’t mean joining the segments just deleted the sustain, I couldn’t add sustain back afterward either.

Restarted the app repeatedly, sometimes there would be sustain for the first five measures, when I would try to edit it to stretch across more of the track it would just delete again.

Sustain can be added to other tracks perfectly fine, it seems to exclusively affect the specific track. I even ended up uninstalling and reinstalling GarageBand in the vague hope that would fix it, but of course that didn’t work either, instead I just lost all of my custom keyboards (thanks apple, very cool), fortunately I backed up the music itself.

In short: sustain magically disappears on a track despite using it the entire duration of recording with no issue, and I can’t add it back no matter what I try, effectively ruining my entire song.

Note: I don’t use any third-party extensions, nor any external hardware.