@Scott R: Can you reproduce the problem in a stock install with a fresh config?
I wonder if you have a custom macro innocently doing something similar to what I did. See
here for details. The save_pos/restore_pos and _save_pos2/_restore_pos2 functions do not save or restore the scroll state. So if a macro saves, then calls any function that directly or indirectly exits scroll, and then restores: the scroll state is not restored, which can result in the vertical scroll position changing.
I can't tell if you're saying the cursor line actually changes, or if just the scroll position changes. If the cursor line is changing, then there are some similar sequences of calls that can result in a macro accidentally changing the cursor line when it didn't intend to.
I can't follow what you did, the description is vague and abstract. Concrete details would be helpful. If you're a developer, then aim for the kind of repro steps that you like to see when a tester files a bug against your code.
Another time I simply moved the scroll bar down, same result as using the mouse or keyboard.
What does the first clause mean? Do you mean you clicked on the scroll thumb, and dragged it down 1/2 an inch?
What does the second clause mean? Do you mean that doing that step, plus some unspecified steps achieves the same result as doing some other unspecified steps that involved the keyboard? I wish I could see over your shoulder, I don't know what these steps are.
FWIW, the scroll bar does move when repositioning using either mouse or keyboard.
I don't know what that means. Do you mean that if you start at the bottom of a file and the scroll thumb is at the bottom of the scrollbar, and then you hold down the keyboard Up arrow and scroll all the way to the top of the file, that the scroll thumb stays at the bottom of the scrollbar instead of moving to the top?
B) I used the mouse to navigate back and forth.
Used the mouse how, exactly? I must not be using the mouse the same way you do. Sorry, I'm lost trying to follow the description of how to reproduce the problem.
Suggestion:Can you pick one specific way to hit the problem? Try it in a stock install with a fresh config. If it occurs, write detailed repro steps for it. If it doesn't occur, then either start checking your macros, or start adding config options until it starts to repro again.