AI can't figure out the building levels

Hi. I’ve created an AI enemy and all the senses are working great. It can follow me if he sees me and it can hear my footsteps. The problem is that, I have a building with stairs and I can go under the stairs. AI can’t figure out where I really am; under the stairs or on the stairs. The same problem is with the first and the second level of the building. If I’m on the second level and AI can hear my footsteps and if the AI it’s in the first level of the building it doesn’t go on the stairs, but it’s moving to the exact point but on the first level.
As you can see in the image, the AI it’s exactly under me even if the target location it’s on the second floor.