When I started DiscordCore, Ill get the error, but its stop working sometimes..

[Discord Core] WebSocketError: System.InvalidOperationException: Collection was modified; enumeration operation may not execute.
  at System.ThrowHelper.ThrowInvalidOperationException (System.ExceptionResource resource) [0x0000b] in <fb001e01371b4adca20013e0ac763896>:0 
  at System.Collections.Generic.List`1+Enumerator[T].MoveNextRare () [0x00013] in <fb001e01371b4adca20013e0ac763896>:0 
  at System.Collections.Generic.List`1+Enumerator[T].MoveNext () [0x0004a] in <fb001e01371b4adca20013e0ac763896>:0 
  at System.Linq.Enumerable+WhereListIterator`1[TSource].MoveNext () [0x0004e] in <351e49e2a5bf4fd6beabb458ce2255f3>:0 
  at Oxide.Ext.Discord.DiscordClient.CallHook (System.String hookname, Oxide.Core.Plugins.Plugin specificPlugin, System.Object[] args) [0x0008c] in <618cbb3cd1f24a338ef71fa504209e7a>:0 
  at Oxide.Ext.Discord.WebSockets.SocketListner.SocketMessage (System.Object sender, WebSocketSharp.MessageEventArgs e) [0x00c5c] in <618cbb3cd1f24a338ef71fa504209e7a>:0 
  at WebSocketSharp.Ext.Emit[TEventArgs] (System.EventHandler`1[TEventArgs] eventHandler, System.Object sender, TEventArgs e) [0x00009] in <45c13f2b01574d8b82248736e42013a4>:0 
  at WebSocketSharp.WebSocket.messagec (WebSocketSharp.MessageEventArgs e) [0x00003] in <45c13f2b01574d8b82248736e42013a4>:0 
An exception has occurred during an OnMessage event.​

This error is coming from the Discord Extension. You would see an error above this stating this. DiscordCore just outputs the error that happened.

ok, how can I fix. Do u have any idea?

Typically reloading DiscordCore should work. It's some weird issue in the extension while connecting the bot.

[Discord Core] WebSocketError: System.InvalidOperationException: Collection was modified; enumeration operation may not execute.
  at System.ThrowHelper.ThrowInvalidOperationException (System.ExceptionResource resource) [0x0000b] in :0 
  at System.Collections.Generic.List`1+Enumerator[T].MoveNextRare () [0x00013] in :0 
  at System.Collections.Generic.List`1+Enumerator[T].MoveNext () [0x0004a] in :0 
  at System.Linq.Enumerable+WhereListIterator`1[TSource].MoveNext () [0x0004e] in <351e49e2a5bf4fd6beabb458ce2255f3>:0 
  at Oxide.Ext.Discord.DiscordClient.CallHook (System.String hookname, Oxide.Core.Plugins.Plugin specificPlugin, System.Object[] args) [0x0008c] in <618cbb3cd1f24a338ef71fa504209e7a>:0 
  at Oxide.Ext.Discord.WebSockets.SocketListner.SocketMessage (System.Object sender, WebSocketSharp.MessageEventArgs e) [0x00c5c] in <618cbb3cd1f24a338ef71fa504209e7a>:0 
  at WebSocketSharp.Ext.Emit[TEventArgs] (System.EventHandler`1[TEventArgs] eventHandler, System.Object sender, TEventArgs e) [0x00009] in <45c13f2b01574d8b82248736e42013a4>:0 
  at WebSocketSharp.WebSocket.messagec (WebSocketSharp.MessageEventArgs e) [0x00003] in <45c13f2b01574d8b82248736e42013a4>:0 
An exception has occurred during an OnMessage event.

Saw this when i stated up my server, not sure what it means