Do you have the tailgate assist? Likely the shop misrouted the wire loom and the pistol and arm hit it. Easy fix to move or pull away with with a zip tie.Like others stated, lithium grease.
Had a shop install a tail/blinker/stop light combo and they had removed my tailgate to remove the bracket that I believe keeps the tailgate from slamming side to side when off-roading. Thay had to get that bracket of to be able to install the light.
Anyways my tailgate now clicks whenever I open or close it and I'm positive it's on the right side.
Not sure what would cause this but I'll have to probably take off the tailgate to see what's going on.