Hi Glamastro
after every OS update it is mandatory to execute a CLEAR SETUP, which is always requested by the unit on the display right after installation. This is important as it resets a number of system parameters and caches for the best use.
Try a CLEAR SETUP powering the unit on while pressing & holding the SETUP key.
If the problem continues, then it may be time to change the internal battery.
lets us know!
best
I
