Upon update to Sierra I'm finding that my wallpaper is set back to the default Sierra wallpaper at every reboot. The correct wallpapers are selected in System Preferences, but they are not shown. I find that I have to go into the wallpapers, select a new one and then immediately pick the desired one again.
This is annoying when you have several monitors attached and have to do this for each one at every reboot.
Any idea on how to resolve this?