We bought a tow vehicle with a 5th wheel hitch already installed. It is a Pullrite Superslide 18k. We bought a used 5th wheel from an rv dealership. They hooked the 2 together. We drove to an rv park (150 miles). Tried to unhook. Could not unhook. The next day we continued to Camping World in our hometown to have a washer/dryer installed.. Still could not unhook. WE TRIED EVERYTHING. The next day, even the Camping World service department could not get it unhooked and they sell these hitches there. We have called Pullrite and they had no answers either. We have owned and lived in 5th wheels many years (with other 5th wheel hitch brands), and NEVER had any problems. Any ideas/similar experience?