In the first class at ABA, when they're doing whatever across the floor, before they start, Anna is behind Jody, because she talks to Maureen. It cuts to them actually going across and Anna is in front of Jody, because Jody crashes into her.
This isn't a slip-up, because she moves in front of Jody. But it is a slip-up when Jody runs into Anna, because it's Anna's fault that Jody runs into her but Jody gets yelled at.