UBPorts Community Edition Pinephone - screen "rotates" even when not rotated.
I seem to be able to reproduce this consistently - but it takes time to encounter this. I typically run Morph browser and let it play a youtube video. I just leave the phone on a flat surface with no movement whatsoever. In about 5-10 minutes, the screen changes from portrait to landscape automatically. I have not had a chance to test this on other distros yet.