CER

Also happens without any players currently being online, or recently disconnected:

[01:03:41] [Server thread/INFO]: USERNAME lost connection: Disconnected
[01:03:41] [Server thread/INFO]: USERNAME left the game

 Last player online left, then this error happens multiple times, here's one of them, no player activity since 01:03:41

[10:06:22] [Netty Server IO #28/ERROR]: Error sending packet clientbound/minecraft:disconnect
io.netty.handler.codec.EncoderException: Sending unknown packet 'clientbound/minecraft:disconnect'
        at knot/net.minecraft.class_9136.method_56426(class_9136.java:47) ~[server-intermediary.jar:?]
        at knot/net.minecraft.class_9136.encode(class_9136.java:14) ~[server-intermediary.jar:?]
        at knot/net.minecraft.class_2545.method_10838(class_2545.java:26) ~[server-intermediary.jar:?]
        at knot/net.minecraft.class_2545.encode(class_2545.java:12) ~[server-intermediary.jar:?]
        at knot/io.netty.handler.codec.MessageToByteEncoder.write(MessageToByteEncoder.java:107) ~[netty-codec-4.1.115.Final.jar:?]
        at knot/io.netty.channel.AbstractChannelHandlerContext.invokeWrite0(AbstractChannelHandlerContext.java:893) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.AbstractChannelHandlerContext.invokeWrite(AbstractChannelHandlerContext.java:875) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:984) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:868) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.ChannelOutboundHandlerAdapter.write(ChannelOutboundHandlerAdapter.java:113) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/net.minecraft.class_2535$2.write(class_2535.java:530) ~[server-intermediary.jar:?]
        at knot/io.netty.channel.AbstractChannelHandlerContext.invokeWrite0(AbstractChannelHandlerContext.java:893) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.AbstractChannelHandlerContext.invokeWriteAndFlush(AbstractChannelHandlerContext.java:956) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:982) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.AbstractChannelHandlerContext.writeAndFlush(AbstractChannelHandlerContext.java:950) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.AbstractChannelHandlerContext.writeAndFlush(AbstractChannelHandlerContext.java:1000) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.DefaultChannelPipeline.writeAndFlush(DefaultChannelPipeline.java:974) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.AbstractChannel.writeAndFlush(AbstractChannel.java:305) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/net.minecraft.class_2535.method_36942(class_2535.java:350) ~[server-intermediary.jar:?]
        at knot/net.minecraft.class_2535.method_10764(class_2535.java:343) ~[server-intermediary.jar:?]
        at knot/net.minecraft.class_2535.redirect$zzf000$antixray$redirectSendPacket(class_2535.java:796) ~[server-intermediary.jar:?]
        at knot/net.minecraft.class_2535.method_52906(class_2535.java:325) ~[server-intermediary.jar:?]
        at knot/net.minecraft.class_2535.method_10752(class_2535.java:319) ~[server-intermediary.jar:?]
        at knot/net.minecraft.class_2535.exceptionCaught(class_2535.java:170) ~[server-intermediary.jar:?]
        at knot/io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:346) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:325) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.AbstractChannelHandlerContext.fireExceptionCaught(AbstractChannelHandlerContext.java:317) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.DefaultChannelPipeline$HeadContext.exceptionCaught(DefaultChannelPipeline.java:1324) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:346) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.AbstractChannelHandlerContext.invokeExceptionCaught(AbstractChannelHandlerContext.java:325) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.DefaultChannelPipeline.fireExceptionCaught(DefaultChannelPipeline.java:856) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.handleReadException(AbstractNioByteChannel.java:125) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:177) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:788) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:724) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:650) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:562) ~[netty-transport-4.1.115.Final.jar:?]
        at knot/io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:997) ~[netty-common-4.1.115.Final.jar:?]
        at knot/io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74) ~[netty-common-4.1.115.Final.jar:?]
        at java.base/java.lang.Thread.run(Thread.java:1570) [?:?]

Version: 1.21.4 (Fabric)