ViaVersion failed to translate a packet
What it looks like in your log
[ViaVersion] ERROR IN Protocol1_21To1_20_5 IN REMAP OF PACKET
What causes it
Packet translation between game versions broke: an outdated Via plugin, Via installed on both the proxy and the backend, or one player’s client mods sending custom packets.
How to fix it
Update ViaVersion and ViaBackwards, run them on only one layer (proxy or backend, not both), and if one player triggers it every time, suspect their client mods.
Not sure this is your problem? Paste your log and Roastd will tell you which of these it actually matched, and what else it found.
Check your own log