Problem with custom UI node and replaying data

As you can see here, we used a trick to see whether a message is being replayed on the client side (e.g. by a tab switch): add a field to the input msg (i.e. on the client side copy of the input msg). When that field is already available when the watch is triggered, then you know that it is a client-side replayed msg (which has previously been handled already by this watch...). In that case you could get your complete dataset from the server.
But of course it is only a trick...