In my current family's home, I have several levels of construction, one at, one above, and three below ground level, with a single spiral staircase running through them. My Sims can go up the stairs easily, but going down is a complete failure, except for the bottom two levels. Does anyone know what's wrong? Is it that the stairway has walls on its sides on the first below-ground level and at the ground level? Do I need to leave a square open on every side?
I've included the house in question; it uses nothing but standard EA content (some of the components are from expansion packs)