When placing a door on a block you are not allowed to, it will not place it, and drop 2 doors, thus infinite door's. I've only done it on half slab's, stairs and fences however.
MCPE-306
Infinite doors
Resolved
Duplicate
0
Johnson Qu
(Unassigned)
Tablet - iOS - iPod Touch
doors, infinite
0.4.0
Retrieved
duplicates MCPE-23