I followed this video,
I stuck all 5 people and hung them up and the voice said, "Nothing like a few decorations to brighten up the place, a merry achievement to you" and the achievement never popped up. Now it keeps on repeating that quote over and over again. I've tried starting a new campaign, a new agent, joining a friends game and trying to unlocked another achievement but none of those methods have worked. So do I have to delete my save game and start all over again or is there another way to stop this from happening?