The way autoscrolling works with pdf is that when you write page1.6 it will make sure that a small slice 60% down the page will be visible. In your case that area is most likely just barely visible at the bottom of you screen and therefore there will be no scrolling. So the solution for you would be to write page1.7 or page1.8 instead.
You can also cross check by hiding the song list. Now you will most likely see the scrolling at 01:05 as that 60% point of the page will not be visible with this slightly bigger zoom factor.
I know this is a bit awkward but I'm not sure how to do it else. Because users who work with full page height surely only want pagewise scrolling and not to scroll a fraction of a page even if there are scroll command for example for network clients that use full width display. Only modification I can think of right now is to make the slice a bit larger maybe. So for example that when you specify 1.6 the app will make sure that the area between 1.6 and 1.7 is visible.