I had the same problem with my Rockwood 5th wheel. Kept losing connection, wiggle the plug and it would work again. Connections were all good. The problem, even though the trailer plug connected into the truck the electrical connections were just not a good match. I bought a Curt truck and trailer plug set, installed them and no more problems.
DRINK COFFEE--do stupid things faster and with more energy ! Rockwood 5th wheel, Signature Untralite, 8244S
Tow Vehicle: Ram 3500 6.4 litre Hemi.