noob question - collision boundary on staircase

I imported a spiral staircase FBX file. I’m wondering why there’s a “barrier” at the very first step that prevents me from climbing it. I can still walk underneath it on the otherside, so the collision shape seems to be correct - I just can’t climb the stairs, or even jump up on it. Am I supposed to change something, besides the collision drop down setting, where I selected “complex?”

Thank you