How does the door fit in the opening, do you have even gaps all the way around? If so maybe the door has been twisted? It may require you to "bend" the door. Block the door just above the latch and with leverage force the lower portion of the door inward. The upper door frame is fairly easy to bend, just push/pull on it. I'd only do this if you've ruled out hinges and the cab opening. Becareful and try to avoid doing any additional damage to the door itself!