2009 Tundra tailgate clunking

Hi all. I have an annoying clunk coming from the back when I drive on rough roads, especially on gravel washboard. With the tailgate off, there’s no noise so it must be related. I adjusted the latches to be as tight as possible without overloading the handle operation, I took off the access panel and made sure everything internal is as secure as possible, and added some felts on the panel so it is tightly in place. The only thing left I think is the bushing on the hinge. Is there an adjustment for this? Theres a plastic bushing on the bottom right side of the tailgate but it doesn’t show any wear spots. Any suggestions?

I tried loading a video showing the up and down play from my iphone but it says the file has an extension that is not allowed

 

Any chance that bushing is cracked? Mine is long gone at this point, it just hangs by hopes and dreams and the latch. Maybe play with that bushing and see if it's damaged. I noticed mine was cracked when the tailgate was on, but once it was off it looked like there was nothing wrong with it.