Hi Joe,
It's usually easier to help troubleshoot issues if you include an example of the slide. Take out anything proprietary or identifying and put in some lorem ipsum text if needed.
One way you might be able to do it is to put the marker on a layer. You could then have a trigger to hide the layer when the user clicks the marker. That should stop the video from playing. I haven't done a lot of testing on it yet but it is just a thought.
I will create a new story with substitute videos for you to test.
