Keyless remote problem

I have an E-350 and the keyless remote needs to be about two inches away from the drivers door glass to unlock the locks. Been that way since new in 97 (as told by previous owner).. The Ford Dealership told him that it was the racks inside the truck that was causing the problem.. That make sense?
Where is the receiving unit for the remote?

try new batteries and use alcohol to clean the contacts in the remote if that doesnt help try moving the antenna in the vehicle around