Bed rigging issue from separated mattress

Hi guys, I'm sure other people have encountered this before (I think I even have, but it was 2 years ago and I can't remember how I fixed it) but I couldn't find a thread about it. I'm having an issue where I separated the space blanket mattress from the City Living bed and am trying to use that to make mattresses for my bunk beds. I think this is a rigging issue. It seems to be fine in blender and S4S, but when I bring it into the game to test, the animation just doesn't work. Screenshot here, package and blend files linked here.