I'm assuming from the error I'm getting that this is the issue, but if you have a console message that's over 2,000 characters then the Discord API will throw an uncaught exception that crashes the server. I'm not completely sure if this is correct but that's what I guessed, here's the log.

Edit: Figured I'd say I'm using All of Fabric 6 (1.19.2), all I've added to the server is LuckPerms (+placeholderAPI addon), Styled Chat, Styled Player List, and Discord4Fabric.