Ok. I was playing Minecraft pocket edition on my tablet. When I mined a door another door came out as another loot. I thought it was just a part of a feature, but I realized it was a bug. If you mined the upper part no loots appear. If you mined the bottom part of the door another door appears along with the door you mined. It was real annoying because it takes up all the spaces in your inventory. I hope it will be fixed in the next update.