Sorry, not up on all of the changes and apologize...yours has top post, so my comments out in the weeds...
But, interesting to me enough to look and found this one pointing to the OEM negative lead being an issue that causes total power loss
Check it out...might be your issue. Key is total power loss to reset. Nothing else can do that, that I can see. Cam sensor...nope, not over night as it has nothing to do with the power system, other than being a consumer of power
YouTube video on GM negative lead issue