My 2002 Century has, over the last couple of months, started switching frequencies intermittently - usually from Radio 2 to Radio 4. I've cleaned around the unit and re-tuned the stations to no avail. Over the same timespan, but not necessarily related to the frequency issue, the door slides open and may remain open for some time or close itself later. I've checked for reflections etc and there are no obvious culprits. If I power the unit off and then on, all is well for a short period then the problems return. Any ideas?