Hi,
I have a similar issue on my Mi 8 Explorer Edition (ursa)(MIUI 12 | V12.0.1.0).
Updating from MIUI 11 I lost all my speed dial and when I try to add one the dialer app crash.
P.S.: I have done the update from MIUI 11 (stable) to MIUI 12 (stable) by the update app.
Thanks for your time and...