I had the same problem and because of the improper amount of bolts and looseness of one or two of them I had a lot of problems:
1) rail bent which caused the 5er pin to put pressure on the jaws of
the hitch (Reese 16K)
2) caused the hitch to release after proper hook-up, bent rails of
truck bed and tailgate.
3) slider did not work and was jammed and had to use pry bar to
get the slider free.
4) Camping World in Tampa told me not to pull with that hitch.
5) Had to purchase a new slider, went with a Pro-glide slider.