Unsurprisingly, the under-display fingerprint sensor on the mid-range Pixel 6a has problems
The newly released Google Pixel 6a
When the Pixel 6a was released last week, many noticed a slight improvement in the fingerprint sensor under the mid-ranger’s display compared to the ones on the Pixel 6 and Pixel 6 Pro; the first word was that Google had used a new source for the Pixel 6a’s biometric reader. Even if that was the case, a major bug has been discovered. The fingerprint sensor on several Pixel 6a units allows anyone, and we mean anyone, to unlock the device.
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He went on to say, “The fingerprint sensor is in the screen, just like on the regular Pixel 6. I scanned both of my thumbs so I can unlock my phone with my right or left hand. My phone, however, lay flat on my side. desk and I decided to unlock it and accidentally used my index finger and pressed the little fingerprint icon on the lock screen. And it worked????”
If this happens to your Pixel 6a, try this workaround and let us know if it helps!
Another Redditor wrote that his wife was able to unlock his phone even though only his prints were registered on the device. And while he only registered his thumbs on the handset, the other fingers unlocked the device. He stated: “Yes, I let my wife try it and she opened my phone in about three tries. Only my thumbs are registered and I have almost all other fingers to work, even cleaning the phone between attempts. Both before and after applying screen protector.”

Even fingers that are not registered on the Pixel 6a will unlock the device on different units
And another post, this one written by “Remunos_Redbeard” says: “Lots of people are reporting the problem, in tech articles and here in Reddit now that they’ve been sent. Widespread problem, unfortunately. I can unlock my friend’s 6a, although my fingerprint is not registered and I’m afraid mine will do the same when it arrives. So at least stick to using a PIN, password or pattern to unlock for now. And definitely don’t use fingerprint for banking or payment apps.”