I have noticed this glitch a while ago. This is a way to dupe items.

Step 1: Place item(s) in chest
Step 2: Exit chest and pause the game
Step 3: Re-enter the chest and take the item(s)
Step 4: Exit minecraft while in chest
Step 5: Start minecraft again, go into the affected world
Step 6: Take item(s). Now you have the double amount of items
Step 7: Repeat steps 1-6
Step 8: ???
Step 9: Profit