For some specific file lengths the scrolling by dragging the minimap stutters a lot. Going back and forth very quickly.
For me it triggers when the file has at least 62 lines to something like 65 lines.
It may be related to the height of my viewport being 61 lines. (Windows 7, 1680x1050)
So it may be reproducible by creating a new file with all the lines of your current viewport filled (with just one letter, it does not matter) + 1 or 2 lines and dragging the minimap.
You will se the minimap jumping back and forth, which is very annoying.