Question Laptop screen flashing black, only during gaming

Oct 6, 2019

I have a Dell XPS 13 9370 laptop, and this problem started recently, maybe after some big Windows updates. All the drivers are completely up to date according to Dell's bundled software.

When playing a game (any fullscreen or borderless fullscreen game it seems), the screen will flash black a couple of times in quick succession every 1-2 minutes. It doesn't seem interfere with the running of the game at all, but it drives me nuts. This happens in very lightweight games like Slay the Spire, so the laptop is stone cold and not stressed.

My only clue is that if I cause the volume bar to appear by touching the volume keys, it seems to cause the black flash (at the instant the bar appears then disappears again). So I think it might be overlay related somehow... so I disabled the Steam overlay, and all that Windows game bar stuff, but it hasn't helped. I don't have RivaTuner or FRAPS or any other overlay thing I can think of.

It doesn't happen in non-game stuff like fullscreen Netflix.

I can't see anything running in the background that would cause this - I've shut down as much as I can.

Any thoughts?