Hey there!
Nice to meet you! I'm Randy, an Independent Advisor.
That’s really frustrating. If your wallpaper keeps going back to the default, even after you turn off syncing and backup, here are a few things to check.
First, go to Settings > Personalization > Themes. Sometimes Windows auto-applies a theme that resets your wallpaper. Try setting your wallpaper again and then save it as a new theme.
If you’re using Windows 11 Pro or a work computer, Group Policy might be forcing the default wallpaper. Press Win + R, type gpedit.msc, and go to User Configuration > Administrative Templates > Desktop > Desktop. Make sure “Desktop Wallpaper” is set to Not Configured.
Next, check your background settings. Go to Settings > Personalization > Background and make sure it’s set to Picture, not Slideshow.
Also, virtual desktops can be tricky. Windows 11 doesn’t fully support different wallpapers for each one. Changing the wallpaper on one desktop might reset it on all. Try using the same wallpaper across all desktops.
Best regards,