At least it is what it seems by using sensor testing apps. And this makes it impossible for the phone to get its orientation (compass is not working).
Screen rotation is still working fine though.
Here is what happened exactly: not long ago I was using Google Maps, but the phone was a bit sluggish so I decided to reboot it.
After rebooting I opened Google Maps again and immediately noticed that the orientation indicator was missing (the blue "beam"), while it was present before the reboot. But I didn't care about it, and just thought that the compass needed re-calibration.
After a few days the orientation indicator was still missing, and the phone never asked me to re-calibrate, as it used to do before instead.
Then one day I launched Google Sky Map, and noticed that the view does not rotate automatically.
So I fired up a sensor test app I had installed (asd.vector.sensor), and no data is displayed for the Gravity sensor. Also orientation is not displayed and the info says that the gravity sensor is used to compute orientation, too.
Other sensors are ok, and as I already wrote screen rotation still works great.
Any clues about this issue? Did anyone ever experience this?
I'm afraid a system restore would not help...
I'm using Resurrection Remix ROM, Android 6.0.1.