New Random reboots or shutdowns since update to MIUI 12: Mi Mix 2 (chiron)

[Business_Kokuna]

Since the update from MIUI 11 to MIUI 12 I face the problem that my device randomly shuts down or reboots. I had the latest TWRP from playstore. I installed the latest specific TWRP for my device (https://dl.twrp.me/chiron/) and tried to flash again. Didn't work. Of course I always did the clean flash (I did the whole thing with full wipe, factory reset, data wipe, clean Dalvik/Cache, system, etc.). Non of the weekly MIUI 12 updates fixed my problem. Please help!

Edit: should I consider to install the Global ROM?