I had a 4 Million BC (sorry I sold it now) and had similar problems. One of the best things I did was to go through all the wiring in the back box by methodically tugging one each wire that is soldered. I was surprised how may were hanging on by a thread. Reflowed the solder on those connections that were questionable and never had any further problems. It is not as bad a job as you might think, took me only about an hour to an hour and a half.