It’s likely overheating. Check the voltage out of the transformer as it’s specced for 24V +/- 10%. And lower the LCD brightness level in settings. I have lowered mine from 6 to 3, but don’t have enough playtime to see if that will do it.

on one machine I can see heat being an issue as the dongle is rightl above the transformer. The other should not be an issue, but we will see if I can reproduce it this week.