I would try a temporary ground on the easiest light to get at. IF that cures it you could make a permanent ground and not disturb the original wiring. My best guess would be the problem is in the area of the fan because most likely it is pulling the most amps.
I suppose if the temporary ground does not help it has to be on the positive side so you might could somehow run another wire without tearing out the ceiling.
Another thought is have you nailed or screwed anything into the wall or ceiling recently that may have punctured the wiring?
I was hoping someone had a wiring diagram for the Elkhorn because as a owner of one I would like to have one also. Fleetwood did not respond at all when I requested a diagram several weeks ago.