I had the same problem with the dually brackets on my camper. The pin on one hinge was very difficult to lift or to drop back down. I removed the pin, cleaned the bores and cleaned and re-greased the pin. When I reassembled everything...voila! ........it was exactly the same!
I removed the hinge from the camper to have a more thorough inspection and, to my surprise, found the pin would now freely lift up and down. As it turned out, the sidewall of the camper where the hinge was mounted wasn't perfectly straight and when the lag bolts were tightened down was causing the hinge to flex enough to bind the pin. No amount of cleaning or grease would help. I installed some shims between the camper and the hinge to allow the hinge to align correctly and that fixed the problem.
2017 Ram Laramie 3500 SRW, CTD 385/900, Aisin. Crew Cab, 4x4
2019 Wildcat Maxx 28RKX