Failed to invoke Method ChatManager:SendText

What it is? and how to fix it?

Code:

Failed to invoke Method ChatManager:SendText with 2 parameters: авпавпав, Sender: Player Client (11), timestamp: 17242.261
System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> System.ArgumentException: The string contains invalid surrogate pair character at 5
  at System.Char.ConvertToUtf32 (System.String s, Int32 index) [0x00000] in <filename unknown>:0
  at Pathfinding.Serialization.JsonFx.JsonWriter.Write (System.String value) [0x00000] in <filename unknown>:0
  at Pathfinding.Serialization.JsonFx.JsonWriter.Write (System.Object value, Boolean isProperty) [0x00000] in <filename unknown>:0
  at Pathfinding.Serialization.JsonFx.JsonWriter.WriteObjectPropertyValue (System.Object value) [0x00000] in <filename unknown>:0
  at Pathfinding.Serialization.JsonFx.JsonWriter.WriteObjectProperty (System.String key, System.Object value) [0x00000] in <filename unknown>:0
  at Pathfinding.Serialization.JsonFx.JsonWriter.WriteObject (System.Object value, System.Type type, Boolean serializePrivate) [0x00000] in <filename unknown>:0
  at Pathfinding.Serialization.JsonFx.JsonWriter.Write (System.Object value, Boolean isProperty) [0x00000] in <filename unknown>:0
  at Pathfinding.Serialization.JsonFx.JsonWriter.Write (System.Object value) [0x00000] in <filename unknown>:0
  at PostToSlackREST.PostMessage (System.String message) [0x00000] in <filename unknown>:0
  at ChatManager.SendText (System.String text, uLink.NetworkMessageInfo info) [0x00000] in <filename unknown>:0
  at (wrapper managed-to-native) System.Reflection.MonoMethod:InternalInvoke (object,object[],System.Exception&)
  at System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) [0x00000] in <filename unknown>:0
  --- End of inner exception stack trace ---
  at System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) [0x00000] in <filename unknown>:0
  at System.Reflection.MethodBase.Invoke (System.Object obj, System.Object[] parameters) [0x00000] in <filename unknown>:0
  at #=qdOCccKsXCENJ9qtwQM1$fTAPYexakK6D3KmUuKhiFWk=.#=q8mOJmxLPFyyFGkGXlkRYtA== (System.Object #=qHb38bdS59HEX_PXCg5OGDA==, System.Object[] #=quonTxdkUuvD6dahY