Every once in a while, I'll wake up my SP6 to find that my lock screen wallpaper is gone and replaced by a solid blue background. All it takes to get the wallpaper back is to enter my PIN to log in, right-click on the desktop, click on Personalize, Lock screen, then select another wallpaper, then re-select the missing wallpaper. I can then put the SP6 to sleep, then wake it up and my wallpaper is back as it was before it went MIA. Anybody know what might be causing it to go away occasionally? It's not a showstopper, just an irritation. It's running Win10 home build 1809 on i7/8GB/256GB SSD.