After a full day of not listening, especially to "stop" commands. We informed Brock that we were upset and that "stop" wasn't working. He needed to tell us what words we needed to use to get him to stop doing the things that he was doing. He said "Stop - Yes - Please".
And this worked. The interesting part is that the order is specific. He would frustratingly fail to stop if we would say "Please Stop", or "Yes, Please stop".