Apple Pro Display XDR goes black intermittantly

Happening more now. went black and would not come on at all without hard restart. Thought it was the Corning optical TB3 cable connected to the computer, so I swapped back in the TB3 cable from apple. That didn't work either until I forced a restart; so seems to be the computer itself and not the XDR monitor.

Any other ideas?

shouldn't be. No hot corners set, and this is in the middle of working, so lot of keyboard and mouse use.

Start after was set to 20 mins. I'll set it to start never and see if it continues to happen.

Mac Pro 2019, macOS Catalina 10.15.6 AMD Radeon Pro 580X 8GB.

I'm trying it without the Corning Optical Thunderbolt 3 cable for now to see if it is the cable. Will have to use for several days and see if it happens again on the copper TB3 cable.