iPad (7th gen) randomly changes screen brightness

I have a 7th generation iPad that's only about 6 months old, and it randomly changes the screen brightness every half hour or so. Automatic Brightness is definitely turned off. This doesn't seem to be affected by a particular app, either.

I've done all the basic troubleshooting such as a hard reset and multiple OS updates. I'm currently running iOS 14.1 but this started happening before I updated the other day.

The brightness will change to seemingly random levels (sometimes almost-full brightness, sometimes almost-off, sometimes in between). The iPad has not suffered any drops or water damage.

Any thoughts?