I wrote about the Knightscope K5 security robot about 6 months ago. Recently, a K5 deployed at the Stanford Shopping Center in Silicon Valley failed in its mission of protection when it accidently knocked down a 16-month old boy and then rolled on.
Obviously our robotic companions still need some work and the software/sensor suite need to be tweaked to improve operation among humans. This is relatively early in the K5 deployment, so I would expect it to improve.
I guess mistakes are expected, after all, the property managers are only paying $6.25 an hour to rent the robot. My personal experience with humans making a low wage like that is that mistakes are common place.