PMA 980 with ADD

I have a PMA 980 integrated amp which I love. In in the past few years, it has developed electronics ADD. That is, the input selector and less often the speaker selector occasionally start jumping around for no apparent reason. It is set to, say, CD. I will listen for anywhere between 2 minutes and 2 hours, then the selector starts jumping around - click, click, click - between Aux, Tuner, CD, Phono, etc. etc. I can somewhat relieve the problem my rotating the knob around a bit, then back to CD. Sometimes that works for an hour; sometimes it works for a minute. Again, it does not happen every time, and I cannot see any pattern to the error. I took it to a local repair shop and they ran it for 2 days and said they never saw the problem; can't diagnose, if they can't see the error... like so many car problems. They suggested maybe ambient IR was hitting the remote sensor, so I covered it with electrical tape... no improvement. Has anyone seen this same problem? If the error is in the switch itself, can I get a new one? I truly appreciate any/all assistance