My '00 16k Reese manual slider wouldn't slide smoothly when new unless I put the NV5600 behind the Cummins in 1st gear and dump the clutch.
I took the hitch apart and cleaned the usual white spray on gunked up grease off.
I greased the pins inside the rollers and sprayed the outside of the slider tubes (square) and rollers with a HD greaseless spray. The hitch worked like a hot knife through soft butter. I power spray at the car wash one or two times a summer and respray when dry. Never had to drop the jacks and take weight off the hitch like some of our earlier sliders were required to do.
I respray 5-6 times each season. If I'm parked on a small incline and flip the lever it slides aft by itself.