Maybe due to the nature of how you got the roboports to occupy the same space as other entities it's possible...and easily accidentally done...to place multiple roboports on top of eachother. This is especially true if you have them blue printed.
I had my electric grid printed out with the roboports on top of electrical poles. When I would expand my grid and I lined up one edge of the print to the exiting power poles so it lined up it would place a duplicate roboport. Once I figured it out I had some locations with 4 roboports. It was an expensive mistake.
