RVing Drives Me Nuts ---- Electrical Issue

Drop one of the lights in question, Or if you can just open the lens and pop a bulb out do that. Use a cheap 12 volt test light to see if it lights when contacting the connectors at the bottom of the socket. If it does, drop the whole fixture out if you already have not. Now put the bulb back in and check the wire in and wire out with the test light. If it lights up on both wires you have a bad ground. Install a new ground wire or find where yours is not making contact anymore.