I was working away when I noticed some of my belt's weren't flowing; I followed them back to discover that a few of my platforms were now completely void of building's.
I went back through my autosaves to see what it was like, and just 5 minutes ago it was all as it should have been. I tried testing to see if I could delate all the building's the same way, but I couldn't do it without also deleting the platforms and belts.