slides are skipped in Preview mode in Captivate 12.3

I have slides in my Captivate project that are basically treated as “hidden” by Captivate. For example – my first slide.  When Captivate starts in Preview (and even in Reviewer mode) it starts from Slide 2. Then, it’s going along well, until it jumps from Slide 4 to Slide 6, even though the “arrow button” on Slide 4 has an interaction to “go to Slide 5”, it acts as if Slide 5 is hidden…. Any suggestions?