Dozens of Pixel owners are reporting that they can't authenticate into their devices because every time they put their PIN in, the phone loops them back to the lock screen. The issue, which was first reported on the Pixel Phone Help forum nearly a month ago, seems to be affecting Pixel XLs the most, though there have been mentions of other Pixel, Pixel 2, and Pixel 3 series devices. So far, product experts have been encouraging affected users to escalate the issue with Google directly or reset their device from recovery.
In all of the cases, the Pixel owners use PIN codes for security and are either on Android 9 Pie or Android 10. When the user enters the correct PIN code and hits "enter," the screen turns black. Users are required to wake the device up again, only to find that they're stuck on the lockscreen. Most times, users can bypass the bug by authenticating their fingerprints, but this would be impossible after a reboot or a long period without authentication.
At least one user has attempted to brute force a failure in the System UI to at least allow an instance of the PIN authentication stage that won't loop over by triggering the emergency call dialer, the volume settings submenu, and through adding a new user to the device. One user was able to get into the settings page, but was not able to enter into the rest of the phone UI.
From what we're able to suss out, if you have a Pixel XL and have not had your PIN working for a bit, you might want to switch your authentication method to a pattern or maybe even a password for the time being. Also, don't wait to be caught in a dead end by lockscreen looping: escalate the issue with Google through this contact page.
Escalation does not ensure a solution, though: it appears Google did not fix a pattern authentication bug for the Pixel C first reported in January 2016.
More details on workaround
Our tipster, Matteo, has commented on this story with more details about how his device works with the solution as described above. In short, he can't write screenshots to the disk and he also can't trigger certain other functions as well.
Another commenter, Terryn, claims that they experienced this issue with a pattern lock, not a PIN lock.
Problem still not solved
This is still a problem and it's not just affecting Pixel phones: an ongoing Google Issue Tracker thread suggests that other Android phone owners are experiencing it as well.
A fleet manager managing 25 to 35 units of the Seuic Cruise 1 on Android Pie had changed their passcode policy and disabled safe boot on all devices and found 2 to 3 units affected by what they found as a null pointer exception. After digging into the specific mechanism, they believed to have found the root cause: the Synthetic Password Key blob, which needs to be decrypted in order for the unlock process to be resolved, is not able to retrieve a stored decryption key — perhaps because it was corrupted at some point. In either case, a null key is generated when the correct passcode is entered and this results in the device looping back to the lock screen.
Other users report their Sony Xperia XZ2 Compact and OnePlus 7 Pro have also been affected by this very issue.
A Google rep acknowledged the issue on September 25 and had passed the thread on to the company's product and engineering teams. As you can tell by this update's timestamp and the continuing feed of complaints, this bug has not been resolved.
This story was originally published on September 23, 2019.