I have the opposite problem. I have a 04 EXT and the tailgate wouldn't open and couldn't get into the bed because of the custom enclosure. The dealership had the truck all week... SORRY JUST HAD TO VENT.
Sounds like a dealer issue.Wonder if anyone else has this problem, my 07 tail gate starts to open but after it gets 1/4 of the way it stops and shuts. I can help it up and it will go all the way but then when it gets to the top it just falls down and can't support itself. Looking to see if anyone else had this problem and what fixed it?