Matt,
I maximized the leadsheet window(have never had to do this before, so I guess that's why I didn't know it was there. The bar does appear at the bottom and I can scroll with that. BUT, I have never done this before in all the years I have been using BIAB. I have ALWAYS simply used the up down arrows(despite what support is saying) that has ALWAYS worked. I would swear that on a stack of bibles.
I just tried it again with the window maximized. I loaded up three or four songs.
The first song I loaded, it didn't work. The second song I loaded(which is the newest song I have created with 2016) worked. I was able to scroll up and down in the leadsheet window with the up/down arrows. And I thought, "great, it's working again". I loaded a couple more...no dice. Went back to the one that was working and it no longer will not work now either.

Even with the leadsheet window maximized the up/down arrow buttons are effecting the chord sheet page(front page)not the leadsheet. It moves up or down in there.

Knowing about having to maximize the leadsheet window will allow me to do that now. But, it is never how I did it before. And have over 1200 songs I have done that way from scratch.

LBL