I have also faced the same problem with Fingerprint issues...... after updating my phone with January Security Patch update, my problem has been solved... Have you try this???
Kindly follow the below mentioned steps to resolve the issue-
> If any screens guard/tampered glass/protection film is available then first disables the fingerprint settings and then removes the screen guard.
> Once screen guard is removed now register the fingerprint again and check the issue
> Make sure to use the central fingerprint parts evenly when you register or scan fingerprint, so that all portions of fingerprint, including the center and corners have been fully scanned.
> If problem does not get resolved, run the device in Safe mode and reconfigure the fingerprint.
> If issue still persists, create data backup and reset the device.
For further assistance, register your concern in Samsung members app (click on “+“icon>send feedback>Error report/ Ask Questions).
