When browsing and editing pages using Magnolia page app, user / we encountered a minor issue with tree view that need us to scroll down to update its UI.
Steps to reproduce, in some browsers you need to do it a bit quicker, sometimes it worked, sometimes it didn't:
Open page app then open 2 or more pages for editing.
Switch to page 1 tab, then close it, we will be redirected to tree view.
Switch to page 2 tab, then close it, you will see that we lost part or whole of the tree view as below image.
Scroll your mouse so that view port get updated and the tree display correctly again.

We can even right click on the remaining part of the page and the view port response with proper context menu, but right click on the missing part didn't get any response.