I was working on a redstone project and then I started noticing a bug with hoppers. The bug is that say there's 15 fences in a chest, (in my case a dropper though) and the hopper is trying to dispense one single fence. Sometimes the hopper would disregard that it could stack it with the 16 fences and just created a new stack.
Duplicate of MC-7650, please use the search function to see if your bug has already been submitted. Currently over 55% of tickets are being closed as duplicate.