Problem with 2 MMs. Both Monitors turns off

[Klinge]

Hello,

I have a problem with my two MMs. Both runs independently.

For both MMs, the monitor always turns off at the same time (MM one every day at about 8 a.m., MM two every day at about 21:30 p.m.) and stays off until the PI is restarted.

The monitor one turns off after about 3 hours after reboot, the other after about 16 hours after reboot.

For both PIs I installed the XScreensaver and deactivated the screensaver.

Monitor one has an installed PIR sensor but the other one does not.

When I connect via VNC, I can see the MM display. But not at the monitor.

I have unfortunately no idea, why the monitor turns off.

I would really appreciate if anyone have a good advice for me.

Thanks in advance.
Lars