Quick Launch Icons Disappear Upon Reboot

I did a clean install, using the Media Creation Tool, of Windows 10 Pro x64 on my Maingear Shift computer (i7 processor, 16 GB RAM) a few weeks ago.  I created a number of Quick Launch icons (to the right of the Start Button), and they have survived several weeks and innumerable reboots as I reinstalled all of my programs.  This morning, out of the blue, (no programs installed for week now) and no changes to the computer of which I am aware, the Quick Launch icons themselves do not appear.  The area of the toolbar, which shows Quick Launch is enabled (you can see the double bars on either side), is there, but there are no icons inside of the Quick Launch area.
 
I have run sfc /scannow and dism /online /cleanup-image /restorehealth from an elevated command prompt.  SFC reported no resource integrity violations, and DISM reported that the restore operation was successful.
 
I also followed the POWERSHELL instructions in this Microsoft article: [URL] .... but it had no effect, though it too reported success.
 
What is interesting is that when I go the left column of the Start Menu, and under "Most Used" and right click on Google Chrome, it shows as pinned to the Taskbar.  When I unpin it, the other five of six Quick Launch icons that I had pinned weeks ago to the Quick Launch Toolbar suddenly appear.  Then I right click the Google Chrome entry in the "Most Used" column again and pin it to the Taskbar and it reappears.  All is well, until I reboot, then it is back to the same old situation of missing Quick Launch icons.
 
I have done a lot of searching on Google, but haven't found an explanation for this behaviour.  I have turned on and off the Quick Launch toolbar, but that has made no difference.  I have warm-booted and cold-booted without effect.