OutOfBounds exception when joining with 1.8.x client -> 1.21.1 Velocity+Paper server

[Kichura]

/viaversion dump Output

https://dump.viaversion.com/38658f2c85c608f64c3d83eaad7c7d237390e7bf37e5a45fc71945f54602bfae

Console Error

No console errors were present during this test run, only disconnect message was given out to client:

Bug Description

When attempting to connect to a Velocity+Paper 1.21.1 server while the client is on 1.8.x, the client immediately drops with a Disconnected message from server while the server gets an OutOfBounds exception.

Steps to Reproduce

1. Create a clean Velocity+Paper 1.21.1 server,
2. Ensure forwarding is either set to legacy or bungeeguard mode,
3. Connect to the server with 1.8.x client,
4. Get kicked immediately after waiting a few seconds.

Expected Behavior

The 1.8.x client does not get kicked out immediately just for joining.

Additional Server Info

1. This server ran on Velocity with BungeeGuard forwarding active,
2. This server ran Paper 1.21.1-132,
3. Via*'s CI builds from Jenkins server.

Checklist

• Via plugins are only running on EITHER the backend servers (e.g. Paper) OR the proxy (e.g. Velocity), not on both.
• I have included a ViaVersion dump.
• If applicable, I have included a paste (not a screenshot) of the error.
• I have tried the latest build(s) from https://ci.viaversion.com/ and the issue still persists.
• I have looked at https://www.spigotmc.org/resources/viarewind-legacy-support.52924/ and it does not offer a fix for my problem

[Barvalg]