Frozen McIntosh MX135 😰

My MX135 froze  :(

All of a sudden I was unable to control the volume or change inputs.  At first, I'd turn it off and turn it back on with the red button and it would be good for a couple minutes.

Then, the red button would not turn off the unit, stopped so I turned it on and off with the black button.  That worked for awhile but not anymore.

Before I brought it to the shop, there were a bunch of @@@@@@@ on the screen.  Of course, the @@@@@@@ did not show up when I brought it in.

It has been in the shop for over a week.  The repair shop regularly repairs McIntosh but is stumped on this one.  He mentioned a system reboot, I think.  He's made calls into McIntosh.

Has anyone experience this problem and how was remedied?  I'd appreciate any input.