Re: Glitches in Next/Previous Button

In the image you provided, there's a trigger for "Item 02" to show a layer. The condition for the Next button refers to "Oval 02." 

Based on that, it appears those are separate objects. If so, some users might happen to click both and, thus, be able to advance, while others only click Item 02 and, thus can't advance. 

If that's not the problem, it's possible that the slide is corrupted. Try re-creating the interactive objects to see if that fixes it.