I've had this happen at two different settlements. When I try to upgrade the Excavation pit to a Ceramics Kiln it builds a Glass Blower instead. I've tried refreshing the plot as well as reloading the save. If I select Glass Blower I get that as expected. In one settlement I was able to finally get it to build the correct upgrade by returning at a later date. That hasn't worked yet for the second, but we'll see. All other plots upgrade to what I select.