also i found this
One guy I know had this issue.
He flashed back to MIUI, created second space, registered Fingerprint and then deleted Second Space. Now it's working for him.
EDIT: yes reboot device too after every attempt of deleting cache
I can confirm that heavy usage still at the end of the day i have like 40%. But if he have battery drain. He can try that and also he can try to go to settings/apps/manage apps/ find system app called miuibiometric and clear data
Clean install here is very discussible term. I make 4 times clean install and he still keep some files. It was very strange im sure that i flush all partition several times. So u maybe can try manualy to do that.
I cant ansver to u becuz i dont use custom fonts but u can try to switch to default theme, reboot phone, then switch to theme with custom fonts then check.