Hi BICSI,
That's a good question! I got curious and created a Storyline project based on your description. My tests show that the motion path was at the end of the animation, picking up where it left off when I jumped back to the main slide, coming from the question slide on another scene. Here's the slide properties page of the main slide:
I attached the sample project so you can look at the slides and triggers.
We'd be happy to look at your Storyline project file if you want us to see how the slides are set up. You may attach your project to this discussion or privately in a support case. We'll delete it when we're done!
