I have noticed several maps in which the height switching buttons on the left don't work exactly as they should. In some cases the buttons are blue, but you can't press them, in other cases the buttons are grey even though the level should be accessible, and in yet other cases there are a several height levels accessible that don't have anything in them. I'll try to list all of those occurrences in this report to make it easier.

The first entry is the map that has a road with a subway below it, and a crumbling multi-floored building. The building is quite high, but the list on the left only allows going to the first floors (you can get to the upper floors only by using the arrow keys or by clicking on the alien count button).