Third-party fingerprint readers may cause lock screen problems

Today I worked on a laptop that couldn't be logged into - entering the password just made the dots spin for a while and the user never got logged in. The machine happened to have some OEM fingerprint reader software enabled to allow fingerprint logons from the lock screen. I found while looking at a Task Manager instance brought up by replacing sethc.exe with a copy of cmd.exe that the Windows Biometrics service was using a lot of CPU. Stopping the service made the logon screen glitch out for a moment, then logging in using a password worked perfectly fine. Apparently the third-party fingerprint logon system is buggy.