Yes I try the button and the Msg was "True".
I also went back to my application and increase the time to 1 second, now I can see how data return is sort of intermittent between the units PLC 1 return data for a few seconds, then switch over to PLC 2, and so on, but never the two of them, I will increase it even more to see if I reach a point where data come to both. Remember someone mentioning before that perhaps finding a way of enable/disable subscription in a fashion that the command don't go out almost simultaneously could be a solution. Obviously I have way more data in each window instance of my application than in your test.
I also set the EnableLogging to True in my application and no data is being logged.