Too many tabs required for keyboard nav

Hi all! I'm having an issue with keyboard navigation in my course. I have customized the focus order for each slide, and in some cases it works exactly like I have it set. But for some slides, you have to hit tab exactly 18 times before the first object is highlighted and can be selected. Before the first object is highlighted, while you're hitting tab 18 times, the whole slide appears to be highlighted/selected. On the slides where this happens, the content varies widely: some have more than 18 objects, and some have as few as 5. This tells me that it's not my focus order that is the problem, but that there's something else going on. Does anyone have an idea what might be causing this? Thanks so much for the help!