1.21.4 client -> 1.21.5 server error

[MelonHell]

'/viaversion dump' Output

https://dump.viaversion.com/6ab7097075d31a787ca6377e25a41a4e61cf68c7b7184f271b84c185a221630f

Server/Client Error

disconnect-2025-04-10_15.21.42-client.txt

Bug Description

InternalServerError
Server IP: mc.emortal.dev
Server software: Minestom
Same problem with local Minestom server

Steps to Reproduce

1. Run mc 1.21.4 vanilla with ViaProxy or 1.21.4 with ViaFabricPlus
2. Join mc.emortal.dev (1.21.5)

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 a build from https://ci.viaversion.com/ and the issue still persists.

[Barvalg]

Athena Log Analysis

Platform Information:

Property	Details
Contains Via	❌
Platform Type	unknown
Is Proxy	❌

[kennytv]

Please send the client logs, too, they'll contain a different error to the disconnect file