The design mistake here is they are cutting the grass as a human would. Computers can bend time to think faster or slower. The way grass should be cut by a robot is very very slowly and continuously. For one thing slow is much more fuel efficient allowing solar power. Also it allows the machines to be made with much less strength and weight. Some day a lawn will be mowed by tossing out 100 little $2 solar mowers that work so slowly you can’t see them move. The slothbots would keep the lawn mowed continuously, never stopping.
Interesting points.