Error While Processing Packet

[piggybxnk]

My friend was trying to join my Aternos Minecraft server, and this error came up. He's joined before with Axiom, and made multiple entities in the world. It just started popping up out of nowhere. He can't join the game at all.
The version we have is 4.1.1 on Minecraft 1.20.4. The version of the plugin on the server is 4.0.1.
We literally tried everything. Even changing the RAM usage on his computer. It's a 4G.
It's weird because I can join the server perfectly fine, and so can my other friend.
Here are the mods we all have:

I'm honestly so lost. Is there a way to fix this?
It's also telling me to update my Axiom to 4.2.0, which there is no download for.
Are we doing something wrong?