Wallpaper Dissappears

I have had an annoying issue of my wallpaper dissapearing at random times. When this occures I am botting up my Mac and login ot find the grey Mission Control background instead. If I try to access Mission Control none of my fullscreen apps or other desktops appear until I scroll through Mission Control. Also I can set the wallpaper when this issue occures but the Mission Control background covers it (I can tell the wallpaper is set due to the translucent menu bar showing part of it). Only way to fix this is rebotting. Any thoughts on why this happens and how to fix it? And just to stop everyone now, the "killall Dock" command in Terminal doesn't work here.