I run manjaro cinnamon with the last LTS kernel (5.4.) (5.5. gives no sound to my HDMI but that's another problem) and nvidia proprietary drivers.
I have my primary monitor connected with DVI and a second with HDMI. The second is actually a TV. I enable it through the "System settings" --> "Display" when I want to use it. Some times, this screen goes black. At this time the running video progresses and the sound continues normally from the black screen. The screen opens again if I deactivate and reactivate it from the settings. But usually if it gets black, it will be again soon after. I haven't notice a specific time before it happens.
I can't tell when this started, but I didn't experience this problem earlier.
What could be the reason for this? What additional information could I post?