Could not Serialize

[kitrick]

Currently running Enigmatica 6 on a modded forge server and one specific player - who has been able to join previously - is continually getting the io.netty error no matter what. Everyone else looks to be able to join, yet it's almost as if they're shadowbanned. Here's the server log every time they attempt to join:

[01:17:17] [Netty Server IO #3/ERROR] [minecraft/ArgumentTypes]: Could not serialize dev.maxneedssnacks.interactio.command.RegistryArgument@4457d8f6 (class dev.maxneedssnacks.interactio.command.RegistryArgument) - will not be sent to client!
[01:17:17] [Netty Server IO #3/ERROR] [minecraft/ArgumentTypes]: Could not serialize string() (class net.darkhax.gamestages.command.StageArgumentType) - will not be sent to client!
[01:17:17] [Netty Server IO #3/ERROR] [minecraft/ArgumentTypes]: Could not serialize string() (class net.darkhax.gamestages.command.StageArgumentType) - will not be sent to client!
[01:17:17] [Netty Server IO #3/ERROR] [minecraft/ArgumentTypes]: Could not serialize string() (class net.darkhax.gamestages.command.StageArgumentType) - will not be sent to client!
[ApotheosisCore]: Patching CombatRules#getDamageAfterMagicAbsorb