)If an inserter (I only tried fast inserters) places an item directly to an underground entrance, the item is sometimes placed on the wrong side. See attached image.
In both cases the items end up on the wrong side. Inserters on the other side of the belt in these cases put items on the same side (e.g. - the correct side), and if the inserters put items on a regular transport belt the items also end up on the correct side.