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NOTE - This has been reported as fixed by Sledgehammer and may no longer be needed. Shoot a few Zombies at the start and quit to make sure it's working before you set out to complete the camo (as you should do for every new gun with the Survivalist camo).
Our Trello Card is specific to a fix released for an issue with these Camo challenges in Multiplayer. However, our friends at Treyarch are aware of this issue in Zombies and are working toward a fix.