Zenon suddenly stopping to fire VariableChange Events

Zenon suddenly stopping to fire VariableChange Events

Using the ZenOn 8.10 interop.zenOn.dll and therefore the COM interface:

I've followed the online help and came to the conclusion that after a few tries (~20), ZenOn stops to fire VariableChange Events. I've implemented the event subscribing like this:

  1. public void SubscribeOnVariableChangedEvent(List<string> variableNames, DOnlineVariableEvents_VariableChangeEventHandler eventHandlerSingle)
  2.         {
  3.                 OnlineVariable onlineVariable = _zProject!.OnlineVariables().Item("OnlineEventVars");
  4.                 if (onlineVariable == null)
  5.                 {
  6.                     onlineVariable =              _zProject!.OnlineVariables().CreateOnlineVariables("OnlineEventVars");
  7.                     foreach (string variableName in variableNames)
  8.                     {
  9.                         onlineVariable.Add(variableName);
  10.                     }
  11.                 }

  12.                 onlineVariable.Define();
  13.                 onlineVariable.VariableChange += eventHandlerSingle.Invoke;
  14.             
Passing in the handler like this:
  1. private void SubscribeOnEvents(List<string> vars)
  2.         {
  3.             zenon.SubscribeOnVariableChangedEvent(vars, VariableChanged);
  4.         }

It works perfectly fine the first few variable changes, but stops suddenly and won't fire the event anymore.
Any ideas on this topic?