1) See if there is any difference when in safe mode: Win + restart
https://www.tenforums.com/tutorials/2304-boot-into-safe-mode-windows-10-a.html
2) Open administrative command prompt and type or copy and paste:
sfc /scannow
dism /online /cleanup-image /restorehealth
3) Consider a system restore to a date prior to the date of the problem.
https://www.tenforums.com/tutorials/4588-system-restore-windows-10-a.html
4) And see if disabling and reenabling the lock screen makes any difference:
https://www.tenforums.com/tutorials/6567-enable-disable-lock-screen-windows-10-a.html
Disable lock screen.
Reboot
Reenable lock screen
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