Why Does My Wallpaper Keep Changing?

I've fixed my problem with my galaxy s5, as just recently my wallpaper kept disappearing and going back to stock screen, well i just went into my wallpaper settings and picked the multi picture live wallpaper i was using before, i think when it did the update it changed the wallpaper settings, it has worked for me so maybe before you do anything major just try and change wallpaper setting back to how you had them, plus do this by the operating system not by the wallpaper app cheers.