FP3 locking itself (screen on) unexpectedly

For the past week or so, after not having this issue sincenit was new in March, my Fairphone 3 will sometimes lock itself, suddenly appearing at the locked but screen on mode. It seems to mostly happen whilst playing games, but also on Chrome and the Google popup browser thing

Tried a factory reset, and reinstall all settings/apps from cloud backup, and did happen once more since when I tested Pokémon Go and a webpage.

Has this happened to anyone else as I can’t find reports? It’s a bit random, not very reproducible except running games busily makes it more likely.

EDIT: last couple times I noticed the top left notifications jump about, one time it seemed to go from Giffgaff to O2, yet I thought it also happened on airplane mode once!?

Thoughts… RAM/CPU overuse issue? Screen loose? Problem with lock/power button? Security setting bug? Can’t decide if seems hardware or software related so what to try!

Some FP3s have a weird touchscreen (“ghost input”) issue. Try this:

Thanks for the input, I wasn’t having too many other random button press screen issues though, just a very occasional missed or double press.

As the service provider displayed in the top left was doing something weird, and then my phone started saying no simcard, I think it may have been dodgy connection with simcard.
I took that out, wiped and reentered it and so far have had half a day without seeing this reoccur.
(If the sim card was pulled out would android lock? No way to test in FP3 as battery blocks from taking it out whilst on)