The Genius Humanoid Robot

Dr. Masuda, a genius professor at the University of Tokyo, has created a state-of-the-art robot that looks exactly like a human. It can accurately identify objects with advanced visual sensors and has perfectly learned the law to engage in social activities. One day, to test the robot's usefulness, the professor sent it to a nearby supermarket to buy apples. However, the robot never returned. Worried, the professor traced its route and found the robot simply standing still at a certain point along the way. Upon investigation, it was confirmed that there were no obstacles blocking the path and the robot itself was not malfunctioning in any way. Why on earth did the robot become unable to move?