There's been some historical cases of this. IIRC it's something to do with the Generator Contactor being faulty. If my memory serves me correctly there was an instance of this in the cruise and the multiple contacts caused the rudder trim to progressively wind in more trim with each contact event.
Perhaps someone here can recall in more detail than me?
Here's the event.
From Skybrary:
http://www.skybrary.aero/bookshelf/books/1686.pdf