A theme switch that plays an intro was giving the shell the new still only if the intro failed. When the intro played, the shell kept the previous theme's background path. The swap deletes that file. When the intro handed the desktop back, the shell tried to open the deleted file and drew nothing. A restart reads the link again, and the next intro can strand the path once more.

The merged command passes the new still on every intro switch, while the background is hidden under the video. If a wallpaper fails to load, the shell reads the link again and switches only when it points somewhere else. If the link itself is broken, it uses the current theme's first background. David Heinemeier Hansson wrote that pointing the background at two missing files, one after the other, recovered to the theme's wallpaper. He opened and merged the pull request.