I will continue to use version 12.9, it's very goodWell, then i dont know, i have MIUI optimization off, 3 days and no more locks of the CPU.
Do you use the "clean all" on the recents screen? I dont use it that much because i found it kinda annoying but i noticed that i had those lock by using it a lot.
BTW as i said, just turn on and off the performance mode and will fix this. I even think that if you just turn it on and off this will never happen again
Thanks you Arthur King