Unable to Set Different Wallpapers per Monitor after using Span

I am currently running a 4 monitor setup, with 3 side-by-side and 1 on top. For a time I was using a Span wallpaper that I created, but now I am switching back to single backgrounds per monitor, but it's only giving me the option to "Set for monitor 4"
Has anyone encountered this problem before?

Have you actually tried it out? Looks like someone forget to set strings.

The 4 "Set for Monitor 4" statements might still apply to monitors 1-4

I have tried clicking them, but they just set the background for monitor 4