MK4 changed update behavior and will not usb update past 5.1.0  

MK4 changed update behavior and will not usb update past 5.1.0

Came home one day to find my mk4 stuck at the loading screen where it shows the firmware version its booting to.  Progress bar was ~99% filled in with just a sliver left.  After a few hours with tech support we got it to accept an older firmware. 

However one thing i noticed was that now the printer will ALWAYS apply any patch it sees on the usb drive without ever prompting, it used to prompt before installing. It will only SUCCEED in installing firmwares up to 5.1.0, all others will get stuck at that same 99% spot.  It doesnt matter if the firmware on the drive is an earlier version or a later version, it will always try to install it on a reboot and only succeed if its 5.1.0 or before.

Now, it WILL allow you to install up to 6.0 (current at this time) via prusa connect, online.  This will succeed every time, which I find odd because as far as I can tell prusa connect is just pushing the file to the usb drive and then telling it to reboot.  BUT the next time  the machine reboots, it will either 1) get stuck trying to load its current version firmware or 2) attempt to install the firmware that the prusa connect downloaded to the card and fail.

I have tried different usb drives and different downloads of the firmware files, no change in behavior observed.

Any thoughts as to what might be driving this?  there was something special about the 5.1.0 bootloader version I think, and I wonder if some bit somewhere is flipped on my board that is causing it to have this weird behavior with respect to updating.  Is my buddy board ever going to be the same or is it otherwise recoverable?