Because of the too important size of the video proving the existence of the bug, I put it on YouTube ! Here is the link : https://youtu.be/TdrT5rhLlUs

I am how going to write how reproduce the bug :

• Use this command :

  /summon minecraft:donkey ~ ~ ~ {ChestedHorse:1,Items:1}

• Then when the donkey was summoned, it is necessary to kill him !

• It gives some leather, and two chests (and a saddle if it has one of it on him) !

• We can get back all the items except a chest !

• The command :

  /kill @e[type=item]

  does not work on this item !

• He can be destroyed with the fire and the lava.