Intermittent problems are the worst kind.
This is not a problem I've had.
I know some people have had the odd problem with the instrumentation and have solved it by disconnecting the battery. Seems to have the effect of resetting all the instruments. It may be worth trying for your radio/satnav.
Your problem may also indicate a loose connection at the rear of the unit. Not sure how to remove it, but it might be worth a look.
Failing that, it sounds as if it might be a job for a mechanic/electrician.

This is not a problem I've had.
I know some people have had the odd problem with the instrumentation and have solved it by disconnecting the battery. Seems to have the effect of resetting all the instruments. It may be worth trying for your radio/satnav.
Your problem may also indicate a loose connection at the rear of the unit. Not sure how to remove it, but it might be worth a look.
Failing that, it sounds as if it might be a job for a mechanic/electrician.