Hello,
As you are working in 3D space, the UCS becomes the main key to place your objects on coordinates. If you did move the UCS and now have xyz on a slope and if you are in fact using AS with Polar Tracking toggled On, it will direct you as it is supposed to, on the xy axis and it will be on a slope if your ucs is placed on a slope. Please do a Zoom All then UCS World. Go on a top view or front view and try to insert a couple of objects, then go on any aerial views and insert columns and beams.
