The HotRodServer allows for the registration of custom ClientListeners that specify a non-existing 'converterFactoryName'. I.e., the ClientListenerRegistry.addClientListener method/function does not check whether the given 'converterFactoryName' exists on the server, and if it doesn't exist, it adds the ClientListener with a Null converter.
The problem is that this gives unexpected results in the client. ISPN in this case seems to send back events that just contain the 'value' of the entry that was inserted/modified/removed. But the ClientListener probably expects a custom type: ClientCacheEntryCustomEvent<MyCustomType>
So, eventually what happens is funky CCEs because the eventData returned in the event (in this case the value of the entry) is not of the same class as MyCustomType.
In my opinion, HotRodServer should return an error when one tries to register a listener which specifies a non-registered converterFactory.