I'm somewhat experienced with Encore and understand the button routing. I've authored many DVD's and this is the first time I've seen this. I have a menu with 20 buttons on it. All of the buttons work correctly except one. I actually have 2 menus like this and it happens that it's the last button on both that won't work correctly. They don't even show up on the preview screen OR when you have the show selected subpicture highlights turned on. The menu just navigates around it like that's how you have it set up in the routing.
OK, I'm not sure why this was happening, but I tried all kinds of stuff here to get these buttons to work and in the end this is how I got around it. On each of my 2 submenus I had one button (the last one I added) that would not work. Meaning when I would preview each menu those 2 buttons were not available to navigate to. I checked, double checked, and triple checked the routing. I even went back and rebuilt each menu from scratch. What ended up working was I added an extra button that had no way for you to navigate to and that allowed the one before it to work. Not sure why this was, but that's what worked.