Camera goes sideways when returning to the camera screen

When you leave the camera screen and come back to it, the camera can show up rotated sideways by 90 degrees, even though the phone is being held upright. Videos recorded in this state also come out sideways.

How to reproduce: open the camera (especially in video mode), record a video or just stay on the camera screen for a moment, switch to another part of the app (like your albums or settings), then return to the camera. The preview appears rotated on its side, and recordings made afterwards are saved sideways too.

Expected: the camera preview and any recorded videos should always match the way the phone is actually being held.

This happens even when the phone is held vertically the entire time. Restarting the app fixes it until it happens again.