I'm having the same problem in all versions. After running on the phone some hours, if you try to reset or power off the phone, it doesn't turn off at all. The screen goes off but the phone is still on. It keeps working. It can be tested turning on flashlight and powering off or resetting it, the flashlight doesn't turn off. It does not turn on again until you force reset by pressing a while the power button. I think it's related to the GPS problem, after some hours the GPS stops working, and this problem also appears.
Using xiaomi.eu 8.7.26 on a Mi 8
Using xiaomi.eu 8.7.26 on a Mi 8