Belts don't stack 'nicely' when changing levels

When connecting a belt from say level 4 to 3, a sloped belt is built. But the same slope cannot be implemented directly below or aboce the original. I've tried to copy the first, raise or lower one level, but when placing above or below a collision message appears. Also, once two levels that contain slopes are in place, with differing slopes, the next layer diverts around the previous.