Just noticed that the scroll indicator does not move while I scroll. (scrolling does work though) When I moved the mouse out of the window and then back, the indicator snapped to it's proper place in the scrollbar. This is on MacOS Mojave 10.14.1 (just updated this morning, I didn't notice this prior to that x.x.1 update, but wasn't paying attention either.)
Are you using Dark Mode?
I am, but on that comment I just tested in Light mode and the result is the same. I noticed though that this didn't happen when I switched to another account. (that was already open) When I switched back to the offending register, it started working properly. Now I can repeat the effect as it only happens on a newly open account. Switching tabs (even to a report, not necessarily another account register) 'un-sticks' the indicator. Closing the offending register tab, even after it is 'un-stuck' and then re-opening, causes it to 'stick' again. Also I tested reports that need to scroll and that indicator works as expected, so this so far just appears to be in account registers.
Not sure if anything was changed, but the scroll bar is working normally now in 3.6-1.dmg. So I'm closing this as RESOLVED-FIXED.