False-negatives occur unmanageably often for 147e:2016 Upek
I have a ThinkPad T520 with 147e:2016 Upek Biometric Touchchip/Touchstrip Fingerprint Sensor running Manjaro. The libfprint version is 1.90.2.
After installing and enrolling, I tried to fprind-verify. The result was verify-no-match. I've tried enrolling and verifying at different speeds, angles, etc. and the next few days the result always stayed the same – verify-no-match. After digging through old bug reports, outdated workarounds and legacy tools, I tried with the left hand. To my surprise it worked! To be honest, my right index and middle fingers have a bit damaged skin but all 10 fingers are still perfectly recognized by my phone. That being said, right now only my left middle finger works more or less consistently with libfprint – about every other time. Other than that my left ring and left index fingers and left thumb kind of work.
I understand that it's an older hardware and it may be quite less capable then the reader in my phone but the levels of false-negatives here are through the roof so I'm pretty sure something is really wrong here. Maybe the acceptance thresholds are too high? How could I better troubleshoot it or somehow inspect the issue?