The bug

When a chest that already has items inside is placed next to another chest, the two visually don't combine. Opening the chest with data will play the animation on the other chest. After relogging, the two will properly combine.

How to reproduce

1. Place a chest
2. Put an item inside it
3. CTRL-middle click the chest
4. Place the newly obtained chest item to the right of the existing chest
→ They don't combine
5. Open the chest on the right
→ The chest on the left does the open animation
6. Close and reopen the world
→ Now they are finally a double chest