I've had a similar experience on my iPhone. The disk became so full that deleting things was seemingly no longer actually doing anything. Rebooting, the phone c

I've had a similar experience on my iPhone. The disk became so full that deleting things was seemingly no longer actually doing anything. Rebooting, the phone couldn't be logged into. Rebooting again, it boot-looped. Rebooting once more, it booted into an inconsistent state where app icons still existed on the home screen, but the actual app was missing, so the icon was blank and the app could not be launched. I became concerned about data integrity and ultimately restored from a backup. I am certain this was a result of APFS being copy-on-write and supporting snapshotting. If no change is immediately permanent, but instead old versions of files stay around in a snapshot, then if you don't have enough space for more snapshot metadata you're in trouble. Maybe they skip the snapshot in low disk space situations, but they still have the copy-on-write metadata problem.