I would check to make sure all of the bolts are tight on the hitch and the pinbox.
We don't get any slop or movement from the hitch to kingpin connection.
The only time we get any 'clunking' noises is when we travel over speed bumps.
Then we will get some movement where the hitch mounts to the rails.
You mentioned having the teflon lube plate - but, you should still grease the kingpin and hitch jaws. FWIW
