Server issue- Failed to syncronize registry data from server, closing connection.

Hello.

I have an issue with my server. I have a modded 1.16.5 Minecraft server. Recently I added some mods to my server and I cannot join because of the error "Failed to syncronize registry data from server, closing connection."

I have checked and all my mods are the same version. My server is on the latest version of Forge. Please help

Log - https://mclo.gs/8h18M4w

I have deleted the config folder but nothing is fixed. I am unsure what is a client log but I think it is the aternos log, that I have given in my first message.

I think it's this-

I deleted the mod and it still appears.

Here-

Server Log- https://mclo.gs/CCRnUAU

However I am now getting a different netty error.

Tried doing that, now the previous error is back.

I read the log and I think it's either the "afoe2019" mod or the "sit" mod. I am not sure though.

I downloaded the "sit" mod and the issue is fixed! I am unsure if this will ever happen again though.