I saw this happen on an episode of cops. Those dogs get really wound up. Cop was arresting the suspect and the dog as unleashed on the side barking, cop puts up his hand and issue a command to the dog, and the dog bit his hand.
It didn’t seem like a serious bite, but I was surprised to see that happen.
Saw something similar happen at a training exhibit where the cop was demonstrating the hold command, where the dog is supposed to circle around the suspect and keep him in place. The cop gave the right command, but the guy playing the suspect was still wearing the padded sleeve used in attack training so the dog reasoned that he’d been given the wrong command, ran across the lot, launched himself into the air, knocked the guy to the ground, then latched onto the sleeve. Funny to watch, but didn’t impress the civic officials all that much.