Doors may take different counters according to the context.
If the owner of a door shop, for example, is counting how many doors she should send to a construction site, she might want to use 枚. I can imagine door panels lying flat on the rear deck of the truck. When treated as something flat and inactive, doors can be counted with 枚.
If doors are already installed in buildings, however, the image of the object changes and, therefore, the counter may be a different one. As the door serves as an area that unites or separates two areas in the building, it is now able to be counted with 箇所, or a place. The mental picture I wish to convey with the counter is, for example, a plan of the building where several doors are marked by circle, "Ah, there is a door here, and here too. And, doesn't that place have a door too?"