"Can you help me fix the wiring on my old trailer?" #%@%^*$_!*#^$*# yeah

I've been beating my brains out trying to figure out what's wrong with my trailer brakes on my car trailer. I did away with the factory installed Scotch locks first thing! I have a Tekonsha Prodigy brake controller in my truck...been there since the truck was new in 04. I have an intermittent code flashing on the controller....NC and sometimes OC. When those are flashing, the brakes on the trailer won't engage. When it has a C (connected) the brakes work fine. I've replaced both the plug on the truck, and the plug on the trailer, and it still does the same thing. I think my next move is to hook to the trailer and take it to the dealer I bought it from to get it checked. They have a gizmo that they can hook to the truck plug, and then hook it to the trailer plug to see which way the problem is. Any ideas? Grey Mousers frustrations kinda hit home....lol.