There is a bug with the document overview on the right/minimap - if you have some text with long lines (word wrap off) and scroll right, the white box around the document outline (if you have that enabled) scrolls off to the right, out of view. Now if you scroll down the document in the minimap, it resets your horizontal scroll position to leftmost.
I would expect the minimap not to reset the horizontal position. I would also not expect the horizontal scroll position (word wrap off) to cause the highlighted area on the minimap to disappear off to the right.
Customer support service by UserEcho