Describe the bug, provide any errors
A player tries to join SkyBlock on 1.8, and they are kicked and an error occurs in console.

How can we reproduce it?
Steps to reproduce the behavior:

1. Unsure, only seems to be happening on this player's island, and we have confirmed that they can join on 1.16.1 normally.

Expected behaviour
The player to be able to join skyblock. Instead, they are kicked and an error occurs in console.
Log of error: https://paste.gg/p/anonymous/f8cdb351ff1f418883d42bc800c31391

Screenshots
None

ViaVersion Dump
https://dump.viaversion.com/c99cfe146be82a9e3a9570de35bb6708c9ca4bb06305c30f2603239d3387bf42