In a case of déjà vu, a minority of Pixel 5 owners are starting to report issues with all of their phone's various on-device sensors, including the compass, gyroscope, and proximity sensor. Based on the details provided, this sounds like the same issue that some prior Pixel phones were plagued by, which may have been caused by a corrupted "persist" partition. However, Google tells us that a fix for several sensor issues across all Pixel devices was included in the December 2020 patch, and some of those affected claim the update fixes their problem.
Reports are few but otherwise consistent, though it still bears repeating: Most Pixel 5 phones don't suffer from this issue, and it's not something we've personally run into here at Android Police. We aren't sure what the ultimate cause is, though we know it could be related to a partition corruption issue. For those that do suffer the problem, most on-device sensors simply stop working correctly, and that can manifest itself in a handful of different ways, from the screen not correctly sleeping or waking when pressed to your ear during calls to auto-rotation failing, or issues with automatic brightness adjustments, or even the loss of a compass in Google Maps, though other sensors including the barometer and accelerometer also stop working.
Odds are you know if this is happening to your phone, given all the tiny things it can break, but if you'd like to test for yourself, most apps that can report a sensor's state should work, including Google's own Science Journal or this random Sensor Test app.
Based on the details, this sounds a whole lot like the issue some older Pixels suffered, in which sensors would stop working as a result of a corruption to the phone's "persist" partition, which holds calibration data required for them to function. In some cases, those that ran into trouble were folks with unlocked bootloaders that had played around with root or ROMs and accidentally damaged that partition (and re-flashing a known good partition image can fix it). However, others that were fully locked and running stock also ran into the problem.
Google tells us that the December 2020 update silently included fixes for a handful of sensor-related issues across Pixel devices, though the related patch notes did not state this (and we're told they may be updated with this information soon). Although the number of reports specific to the Pixel 5 in the wild remains relatively small compared to prior Pixels, some of those affected do claim that the December update solved their problems. However, we have seen reports that rebooting can also fix the problem temporarily in some cases, and the update has only been released for a few days, so time will tell.
- Hale Knox