Netty Server IO #5/ERROR HELP ME PLEASE

I've been trying to run an avatar the last airbender mod on Minecraft for the last few days and I'm not sure whats happening. I've tried everything from reducing view distance to revamping my ISPs settings and im at my wits end. The server is fine until more than 2 people join and then it just times everyone out. Ive also tried randompatches mod and FoamFix as well. This error keeps popping up:

[17:29:52] [Netty Server IO #5/ERROR] [FML]: NetworkDispatcher exception
java.io.IOException: An established connection was aborted by the software in your host machine
    at sun.nio.ch.SocketDispatcher.writev0(Native Method) ~[?:1.8.0_281]
    at sun.nio.ch.SocketDispatcher.writev(Unknown Source) ~[?:1.8.0_281]
    at sun.nio.ch.IOUtil.write(Unknown Source) ~[?:1.8.0_281]
    at sun.nio.ch.SocketChannelImpl.write(Unknown Source) ~[?:1.8.0_281]
    at io.netty.channel.socket.nio.NioSocketChannel.doWrite(NioSocketChannel.java:432) ~[minecraft_server.1.12.2.jar:?]
    at io.netty.channel.AbstractChannel$AbstractUnsafe.flush0(AbstractChannel.java:856) [minecraft_server.1.12.2.jar:?]
    at io.netty.channel.nio.AbstractNioChannel$AbstractNioUnsafe.forceFlush(AbstractNioChannel.java:368) [minecraft_server.1.12.2.jar:?]
    at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:618) [minecraft_server.1.12.2.jar:?]
    at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:559) [minecraft_server.1.12.2.jar:?]
    at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:476) [minecraft_server.1.12.2.jar:?]
    at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:438) [minecraft_server.1.12.2.jar:?]
    at io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:858) [minecraft_server.1.12.2.jar:?]
    at java.lang.Thread.run(Unknown Source) [?:1.8.0_281]

This spams about 20 times before the server jus kicks everyone, please help idk what to do.

Thanks in advance