Trailer lights with a Range Rover

[DonArm]

I hired a trailer on Friday night and had all sorts of problems with the trailer lights. The trailer people suspected the trailer lighting module, so it was removed and the PCB checked for burning. As the PCB looked ok everything was put back together and the supplies in and out of the module got checked. They proved to be ok and the lights got checked with their tester, everything ok. Hooked up the trailer, everything fine. Saturday morning, no lights on the trailer, back to the trailer hire place, repeat of fridays testing, now think the module is totally dead. Anyone had similar problems?