Side bar does not refresh when logged in as administrator and scroll up

Summary

Side bar does not scroll correctly when logged in as administrator on long pages

Environment

• Confluence 5.9.1
• Internet Explorer 11, Google Chrome (latest), Mozilla Firefox (with smooth scrolling turned off) on Mac and PC.
• The operating system is set to jump 2 or 3 lines with page scrolling

Steps to Reproduce

1. Create a page with lots of content, so that the left scroll bar appears in the browser.
2. Log in as administrator
3. Go to the page created in step 1
4. Use the mouse wheel to scroll down three lines
5. Use the mouse wheel to scroll up three lines

Expected Results

The side bar moves down with the page content.

Actual Results

The side bar stays at the top and blocks the menu

Notes

Occurs also with arrow keys, but not as extreme.
Doesn't occur on Chrome for Linux.

Workaround

• refreshing the page

or

• pressing [ twice (it hides and un-hides the side bar)