It does not take much to hang one up. If linkages are working I would guess it is a metal on metal interference. Most likely between the latch in the door and the latch on the cab. Don't know how brave you are but have someone hold the latch down from the outside, put a pillow under your shoes and give it a kick from the inside, it should pop. Tools between cab and door is not the way to go you will quickly damage the rolled edges. Good luck!