Trailer Light Question

Another update on the running lights. The truck was at the dealership getting new tires so we asked them to check out the running light issue. The dealership checked out the system and felt it could be the plug at the fifth wheel hitch that was added when we had it installed. They suggested we use the factory plug in at the hitch on the bumper. My husband didn't think that was the issue, but in order to say he tried everything, he agreed to do that. Well, same issue. So, it has to do with the module in the truck. At least the issue has been narrowed down.