com.miui.powerkeeper, MIUI's battery optimizer. The one that thinks killing a foreground app is ok to free up a few hundred mb of RAM... with 1GB RAM available <_<
Freeze it with SD maid (or any other root app manager)
EDIT: can anyone with a mix3 confirm that the proximity sensor is not working?
If I Kill this "com.miui.powerkeeper" via ADB DEVICES, will there be any boot issue??