I've the same issue too on my Redmi K20 pro premium edition. (MIUI12 v22.214.171.124 stable)
Contact and Dialer app crashes when i want to add a Speeddial Contact or when i try to add a number from WhatsApp to an existing contact.
The 2 other K20 pro from my son and my wife have...
I'm using the actual 12.0.3 stable eu-rom on my K20pro Premium Edition and since Update from stable 11 the Speeddial option crashes everytime i want to add a number.
This happens on 12.0.1 and 12.0.2 too.
Has anyone this problem, or a suggestion how to fix this?