Not sure what is happening here, but both the client error window and the server console showed these error at the same time while not allowing me to log in to my test server. However, I can log in if I attempt a second time. This is an update I am working on for my pack, 99 Mods on the Wall

Thank you,
CM

Minecraft: 1.18.1
Forge: 39.0.5
inventorysorter-1.18-19.0.0

99 Mods on the Wall 1.18 Forge-2.3.0.zip (not ready for publication on CF yet)

Shown in console:
[14:55:41] [Server thread/INFO]: ClaudiusMinimus joined the game [14:55:41] [Server thread/INFO]: Login detected, adding player to logins for defuzz. [14:55:41] [Netty Epoll Server IO #4/ERROR]: Could not serialize cpw.mods.inventorysorter.InventorySorterCommand$ContainerClassArgument@45ef0dd2 (class cpw.mods.inventorysorter.InventorySorterCommand$ContainerClassArgument) - will not be sent to client! [14:55:41] [Netty Epoll Server IO #4/ERROR]: Could not serialize cpw.mods.inventorysorter.InventorySorterCommand$ContainerClassArgument@7cd281d2 (class cpw.mods.inventorysorter.InventorySorterCommand$ContainerClassArgument) - will not be sent to client!

server latest.log
client latest.log
client debug.log

PS: After I posted this I restarted the client and the exact same thing happened, but this time I was paying closer attention to the console and the client.
1.) The client froze for a second
2.) The console printed out the above error.
3.) The client displayed the graphical text error
I hope this helps.

BTW: Thanks for making great mods!

I have disabled the mod for now and the error is gone. Look forward to an update!

This doesn't seem to be my mod specifically, but rather something trashing the entire netty subsystem somehow. Very curious.