Findings after a few of days:
-
Proximity sensor: OK
-
GPS location: Icon is after enable and disable still there.
-
Display auto backlight: changes slow
-
Screen flickering after boot up: from time to time still there
-
FP Open OS: Clock resets after reboot: still there
-
Random reboots: seems to be gone
-
Battery only charging mode: does no longer work on a notebook usb port with max 0.5A.
Summary: Feels more stable - thanks a lot!