Simple enough: I was had a couple of saves of the world in the screenshot, decided to delete them both and make a new save. Deletion worked fine, but couldn’t make a new save. Clearing out the saved games folder didn’t help either. Could not reproduce on a fresh world however.
In the mean time, enjoy the only surviving record of South Ayesong. Two warehouses and a trapper’s home beyond the main structure. The main structure consisted of two towers, a gatehouse, and a couple of L-shaped corner buildings that were being worked on when everything broke. The whole thing was on a two-high raised floor (that had the pathfinding algorithms screaming for mercy whilst under construction, but I digress ).