Storyline Progress Bar Animation - Looking for Ideas

I've checked out your file, and I see the hangup with this particular implementation as a Wipe issue. When a new slide begins, the entire bar that Picture 3 represents is wiping from left to right. For that .5 second, the circular tip disappears because it hasn't wiped in yet. To see more visually, recolor the top progress bar picture on a slide to something like orange:

Then when you preview the slide, you'll see better how the orange bar wipes in on top of the blue bar.

I think the effect you're going for would require something like cropping Picture 3 down to only the length of the increase, not including the existing progress, and animate that from its left position on the prior slide to the new position on the right. Copy-and-paste.

I've fiddled with using Storyline's built-in sliders as progress bars as well as animating one rectangle on top of another with JavaScript. That method allows for smoother animations but isn't for every project.