My problem is the app sends my reading position up to a few chapters back, and sometimes the top of the last chapter I read, so I waste a few seconds everyday scrolling down with the table of content or the sliding bar. It doesn't affect the number of unlocked chapters, though. It started after one of the recent updates, maybe a couple weeks ago.
I have a new problem from yesterday's update where the reading controls go past the edge of the screen, so I can't see all the controls. Happens if tablet screen is set to landscape, goes away if on auto.