Macbook's keyboard lags during password input
I have an early 2015 MBP retina, currently running Big Sur 11.6. Since I upgraded to this OS version, the laptop's keyboard lags while I enter my user password during start up, thus it's not able to read the whole input of the password. I have to enter it very slowly so I can proceed. Then it takes almost 2 minutes to log in. What's the solution for this?
MacBook Pro 13″, macOS 11.6