Issue with step height

I created a 300x300x150 block in blender and exported it to ue4 (as a fbx file). It appears that in the ark mod kit that the ark player model can only step onto my block when it’s 15 units high (possibly more, but less than 25); however, in normal ue4 the actor in the shooter template can step onto my block even when it’s 35 ue4 units high. Furthermore, once I changed the mesh for a stone foundation (which, as far as I could tell, could be stepped onto at least 35 units high) to my new mesh, I couldn’t walk on it anymore.

Is this a bug, and also, where can I find where to edit step height in the ark mod kit? (As I’ve heard that’s what the issue might be, from googling a bit)