I have purchased additional space in my colony, and build an aluminum road around the outer edge of the colony. For some reason, the builders seem to think the outer edge of the colony is not useable. They will build on the edge cells, but will not actually traverse the outer cells. I am using the windows 10 version 0.67.0. This makes it so that if I build something next to the road, the builders will not actually build there, as if they cant get to the new buildings.