The OPC Server has access permissions defined on a per node basis. This also includes configuring for each object if events generated from this object can be received by a certain user or group.
A client subscribing for events (e.g. on the server object) will not receive events if the access permissions are insufficient.

For every other restricted access the client gets a direct feedback from the server e.g. try to read or monitor an item returns BadUserAccessDenied.

Now the problem is that there's no way for a client to see that events where missed because of the access permissions. This can be dangerous if a client relies on receiving all critical events when subscribong to the server object.

We need a standardized way to get the information "event not received because of insufficient permissions".

A good place to put that information may be the server diagnostics.