Yes there's some sort of bug where they're trying to reach one of the un-reachable blueprints causing the route finding to tell them to go to tile 0,0 (top left corner). Thanks for reporting
Ahh I see. I noticed they started to come back at random as other blueprints progressed, so now I figure that's because they could reach their target.
Glad to hear it's on your list, good job with the game guys!