Sim teleports to top of platform instead of using stairs

I'm building a skylight/telescope peephole in my sim's attic, but I wanted it to be functional. I used a platform so the telescope actually peeked out through the roof, and put some stairs down so my sim could get to it. Everything works well, except for one thing. My sim ignores the stairs, instead opting to walk through/teleport to the top of the platform.

I tested it by making her just walk up to the telescope (thinking it had something to do with the telescope's animation) and the same thing happened. I tested with and without mods/cc - same thing. She even teleports when there are no stairs at all! Usually, I wouldn't complain. I'm not someone who really cares about "features" like this "breaking immersion". I personally think it's hilarious, but it still is a problem, no?