I am running Windows 10 Version 1709, OS Build 16299.192.
I am not alone with this problem. From my searches there are thousands of users with the same problem with many, many different versions of the OS.
I have a very long list of folders and disks. If I use the slide down, I probably have about two screens full of such folder and disk names that show in the left pane. As I start to slide down and look for a folder to click on (right click on the angle arrow (i.e. this >), the screen will all of a sudden jump back to the top and show the page starting with Quick Access again.
It doesn't happen every time so I am having a hard time nailing down any kind of pattern.