I have a 2014 gmc sierra with 25k miles that has had this issue since day one.
thought about taking it to the dealer, then realized ...
my fix was/is:
go back to where hotrodz37 shows pics
look under your seat
i used (3) #10 hose clamps @ 79 cents each
i couldnt find the " C " clamps FOR THE RUBBER but i had a strip of rubber 3mm (just under 1/8") thick
cut 2 pieces 5/8" wide x 2 1/4" long
i clamped the rubber in using the hose clamps exactly how the pics show, on the inboard sides of the white stock clamp
rubber on the top of the 1" tube, hose clamp head towards the floor.
crank down using a cordless impact:
first test drive, perfect except felt a clunk pulling into driveway.
added hose clamp with rubber to the "outboard" side of the white stock clamp.
using 3 clamps with rubbers
SEAT NOW FEELS VERY VERY SOLID
hopefully it holds
feels great now, no dealer involved