Shulker boxes not remembering items.

I've been trying to recreate this bug but it's not the only time it's happened.

Shulker boxes don't seem to be remembering items.

Timeline of events:

1. On a shulker-shell/elytra raid in the end-dimension.

2. Couldn't use an ender-pearl in a gate to get back to the main island.

3. Decided to suicide after putting all my things in shulker boxes, and putting them in an ender-chest.

4. Dove into the void.

5. Died, respawned back at base.

6. Items I stashed not in the shulker boxes I put in the ender chest.

7. Tried closing the game and re-opening, to see if that would fix it, but nothing.

Also of note, when I respawned, none of the armour stands were visible, none of my wolves were visible, and neither were any of the item-frames, or chickens in a farm I built. (I could hear the wolves and the chickens, but they weren't appearing.)

What I expected to happen was...:
Shulker boxes should have stored the items I put in there.

What actually happened was...:
Shulker boxes didn't remember the items.

Steps to Reproduce:
1. Unsure what to do to recreate this.