Can someone tell me, whats causing that issue:

20:36 [Info] [Economics] Saving balances for players...
20:36 [Error] Failed to call hook 'OnServerSave' on plugin 'XPerience v1.3.8' (KeyNotFoundException: The given key was not present in the dictionary.)
  at System.Collections.Generic.Dictionary`2[TKey,TValue].get_Item (TKey key) [0x0001e] in <eae584ce26bc40229c1b1aa476bfa589>:0

  at Oxide.Plugins.XPerience.OnServerSave () [0x00050] in <84829b1103a246f58d03a3dd85bfff61>:0

  at Oxide.Plugins.XPerience.DirectCallHook (System.String name, System.Object& ret, System.Object[] args) [0x01973] in <84829b1103a246f58d03a3dd85bfff61>:0

  at Oxide.Plugins.CSharpPlugin.InvokeMethod (Oxide.Core.Plugins.HookMethod method, System.Object[] args) [0x00079] in <60c318df79ed41688ea59335e48d61ad>:0

  at Oxide.Core.Plugins.CSPlugin.OnCallHook (System.String name, System.Object[] args) [0x000d8] in <dfcb48ea05694263bbc08e62a39c274c>:0

  at Oxide.Core.Plugins.Plugin.CallHook (System.String hook, System.Object[] args) [0x00060] in <dfcb48ea05694263bbc08e62a39c274c>:0

This seems to be a random error that is popping up, I am working to find the cause. It doesn't seem to be a constant repeating issue so it's difficult to determain what's causing it.

is there no way to debug this message to find out where it comes / what causing it?