4 cpu's in idle, and why is my phone rebooting when locked?

[abendsessen]

My phone started doing something very strange. As long as I am using it and the screen is on, it works fine, but a bit slower than I'm used to. But as soon as the screen goes off (sleep) or I press the power button to lock/sleep the phone, it crashes and then needs to restart to start working again. I later noticed using some apps that 4 of the cpus are always on idle. But on my other mate 20 pro (own 2) all 8 are working. I have attached images of the faulty, and working mate 20 pro I have.

 

[elgabrymn]

I have the same problem; it reboots as soon as the screen is off. Did you find a solution?

 

[abendsessen]

I have the same problem; it reboots as soon as the screen is off. Did you find a solution?

I didn't end up fixing it, I was told to try things like change the battery first, and if that doesn't work then reboot cpu, and if that doesn't work reball cpu