I discovered that keeping an item in a chest and without closing the chest, if you quit the game. you can have 2 of the items - 1 in your inventory and 1 is the chest. This glitch works almost 90% of the time to dupe items... but at times the items even get deleted.

to reproduce the dupe :
1. take any item in the game
2. as soon as you put the item in the chest, quickly crash/ force quit/ close the game before the net data gets fully updated.
3. now you have 2 items

this glitch can be dangerous on servers and on any world because of duped items circulation.