Have created my first slideshow with all slides containing Video Elements (videos are on Youtube) and it is working fine except that if I start a video in a slide then click Next (or Previous) while the video is still playing the slideshow moves to the next slide but the previous slide's video does not stop playing. If I click play on the next video I have two videos playing at once and so on.
How do I stop the current video playing after advancing to the next slide?

I would have thought that is impossible without manually stopping the video,, otherwise how would the video know when to stop just because it's out of view, the video controls don't know as far as the video is concerned it's still in view.