I don’t have any concrete answers here, but I’ve experienced this a few times on my Mac. All of the times it occurred were after leaving a project open or just Cubase running overnight. Picking up where I left off in the morning (or even restarting Cubase), everything would function “normally” for a while, but eventually I would get a crash an hour or so in. The back up file would always be timed and dated BEFORE I started working. Opening that I would then eventually get a freeze requiring a hard boot of the computer–only that would return everything to normal. I’ve also had strange malfunctions start happening during the freeze that I don’t get any other time, like the timeline not scrolling with the project all while audio is still playing. One time I left and ran some errands to see if it would fix itself, but returning 2 hours later, it was still trucking along in the same confused state.
BTW, I have the machine and hard drives set to NOT go to sleep, so I don’t think that’s it.
I’ve always thought this behavior might be a result/consequence of automatic maintenance scripts the Mac was doing overnight. I run Retrospect and Data Backup BU software which also does it’s thing during off-hours. Perhaps that messes with stuff somehow?
I’ve never had auto-save issues after starting Cubase up fresh in the morning, so that’s always been my routine.