I have only had to fill my D up 3 or 4 times, but every time I do, I can not open the fuel door. I push the button and everything works fine with the release mechanism, but the door won't open. I have to have a family member hit the button while I pry it open with my finger. The only thing I can think of is since the tank has no cap, as the gas is used it creates a vacuum. Since the door does have a seal around it, it hold that vacuum and doesn't open unless pried open. Has anyone else experienced this???