The bug

When you place two chests with custom names next to each other forming a double chest, both chests will keep their custom name and it is based on the direction which name is used.

Expected behavior

When a chest is placed next to an existing chest, the custom name of the existing chest should be set to the custom name of the placed chest.

Same should apply when using /blockdata.

How to reproduce

Name not overridden

1. Place two named chests next to each other

   /setblock ~1 ~ ~ chest default replace {CustomName:"chestA"}
   

   /setblock ~1 ~ ~1 chest default replace {CustomName:"chestB"}
   

2. Use /blockdata to show the NBT data of the chests
   → The chests show CustomName:"chestA" and CustomName:"chestB"

Name direction based

1. Place two named chests next to each other

   /setblock ~1 ~ ~ chest default replace {CustomName:"chestA"}
   

   /setblock ~1 ~ ~1 chest default replace {CustomName:"chestB"}
   

2. Open them
   → The inventory has the name "chestA"
3. Place two named chests next to each other (other direction)

   /setblock ~1 ~ ~ chest default replace {CustomName:"chestA"}
   

   /setblock ~1 ~ ~-1 chest default replace {CustomName:"chestB"}
   

4. Open them
   → The inventory has the name "chestB"