Unit production structures near the slope can cause built units spawn inside the slope and they get stuck there forever. Mouse clicks do not go through slope's texture.
Ape Apps, LLC is an independent software development company founded in 2010 by Brandon Stecklein. Over the years, Ape Apps has published over 400 apps and games across various platforms. You can get in touch with Brandon on Twitter or by leaving a post on his wall @bastecklein