Double finger scroll no longer scrolls as expected

I have my app set to flip pages, so "scroll view" is unchecked.  However, as I quite frequently highlight text, I need the scrolling function to realign the text so everything I am wanting to highlight is on the same page.  

Up until very recently this worked flawlessly by swiping with two fingers up and down, which replicated the scrolling function.  This for me was a brilliant combination and I used it almost daily.  

Somehow after one of the more recent updates this has stop working.  Now doing a double finger scroll, instead of a smooth sliding motion of the text scrolling up and down, it jumps all over the place, a few pages forward and a few back.  It feels very erratic and "glitchy". 

I am using Android app version 5.16.5 on an LG G4.  I can also replicate the issue on my ASUS Transformer tablet.

A two finger salute to anyone who can fix this!