Be on the lookout
Many students interpret the block Reverse Direction as a command to start moving in the opposite direction. Therefore, they expect a robot to continue to move when the Reverse Direction block is executed in a program such as in the program Needed.
What you can do: Tell students that the Reverse Direction command is independent of turning on/off motors. It is not a movement command, but rather an orientation command (prepare to move in the opposite direction). Emphasize that motors will continue to do what they are commanded to.