Error when changing backend server

[MotikaCraft-TheJoshua]

Describe the bug
Plugin throws error sometimes when player switches server or is sent from 1 backend server to another

To Reproduce
Steps to reproduce the behavior:

1. Install protocolize dev build plugin on proxy server
2. Start up proxy server (and backend servers connected too)
3. Join proxy server
4. Send yourself or switch to another backend server via proxy
5. See error happening 1 in 1000 (it's very rare, at least in my case)

Expected behavior
Should not happen

LOGS
https://mclo.gs/aDqUYEd

Proxy environment
FlameCord-2.3.3 & Waterfall for 1.21
Tested with no other plugins

Minecraft versions used
If applicable, tell us the used minecraft client AND server versions that are involved in this problem.

• PROXY SERVER: 1.21+ (FlameCord & Waterfall)
• BACKEND SERVER: 1.21.1 (Paper & Purpur)
• CLIENT: 1.19.4