Default [Q] Google Now Launcher Wallpaper bug

Hi,
I have a problem with the Google Now Launcher. Nothing major. But the wallpapers I set via Gallery > Set as Wallpaper are glitchy and not smooth when I press the Home button. They tend to jump around. But when I long tap on the Home Screen, select Wallpaper and select a picture. it works fine. Can anyone tell me what the problem is?

added a video clip here.
youtu.be/tohai2A0CrY