At the rear tail lights I have running lights but no brake lights or turn flashers. I tested the trailer adapter back several weeks when I first wired it and installed it above the gas tank and all was good. Now body is on and I'm installing the rear square lights and there is a major voltage drop across the adapter. 12.65-ish volts going in to turns both left and right and brake too, but coming out 4.5-ish volts at the turn wires and brake. Hazards don't flash at the back, but the amber front both flash and same for the turn signals, both amber lights are flashing. Bad ground?, bad adapter? Thoughts, suggestions.

Thanks in advance - Fred