I fixed this by tightening the two hex bolts on the center latch (the whole unit had come loose). I just pushed it to the bottom of its slot (furthest in towards the front of the vehicle) and tightened it so that it no longer rattled.


Then, I had to move the rubber bumpers on the sides upward so that the upper half of the tailgate would stop rattling.


Over time, I have only had to raise the rubber bumpers on the side when the tailgate started rattling again. The center latch did not come loose again.


No tape, no tubing, no rubber foam dampeners needed.