Hi,
Just to confirm, the wallpapers are applied correctly to each virtual desktop, but after restarting your computer, they all revert to the wallpaper from VD1. Is that correct? If so, the issue may be related to your theme settings, possibly due to theme corruption. Before looking into that further, have you tried assigning the wallpaper for each virtual desktop using the following steps?
- Go to Settings > Personalization > Background.
- Right-click on an image in Recent images > Set for desktop > Desktop 1/2/3