[Jay & Bobbie]

I put a horse stall mat (from Tractor Supply in the bed of the truck prior to installing the Anderson hitch. Make sure you tighten all bolts to spec, then tighten them again when hitched to the trailer with load on the hitch. This will require loosening the two lower bolts to tighten the top (pull down) bolt, the re-tighten the lower bolts.
Make sure you get the Allen set screws on the trailer kingpin tightened to spec as well.
Grease on the ball does help.
Other than that, it could be the Morryde king pin moving somehow. Watch for abnormal movement when hooking up (changing load from trailer jacks to truck hitch).
FYI, I do like the Anderson hitch, but I am planning on switching to the Reese Goosebox when I can afford it.