I think this problem is not new in 1.6, is it?
I have never considered putting 3 stairs next to each other like this. The hero can only use one of them at a time, so the behavior is expected.
2 solutions:
- You could try making a stairs entity of size 48x16, because in 1.6, all entities can have any size. But for stairs you can only change the size from a script, and more importantly, it was never tested.
- Do you even need a stairs entity at all? You can use sensors instead to change the layer of the hero.