Bella Vida

Had this boat a couple of years and recently it has developed an irritating non persistent fault which is linked in some way to the stereo system, the windlass and GPS Display. The fault occurs randomly when all three have no power and again for no reason may start working again . There appears to be no circumstances which trigger the event, The boat was not bouncing around either when the power to all three stopped and indeed going into the marina at 3kts power restored again. !!!!!!