Since the 1.55 patch, the Hewnsman Spiral Staircase when stacked on top of each other is a bit broken. When going to use the stairs to get to a lower floor, the sims path is blocked. If they climb the stacked stairs all the way to the top and then use the stairs to go to the level they want, then the path isn't broken. Nor is it broken going up the stairs. The other two types of spiral stairs (including the new one with the patch) are not affected and functioned fine in my testing, just the Hewnsman. Tested the stairs in all four rotations and the same thing happens.