In classical conditioning, the rules depend on your dog's emotional state (happy or upset), rather than their specific behavior.
The goal is to change how your dog feels about something. Because of this, you should immediately Drop at the first sign that your dog is upset.
Don't worry about dropping frequently in the early stages. Building trust is far more important than speeding through the plan, and it is much harder to rebuild trust once it has been broken. Moving faster than your dog is ready for will slow down your progress in the long run. Ironically, you will reach your end goal much faster if you move at what feels like a snail's pace.
If you fail a single rep then Drop Unless the step has already been repeated then Split If all reps are completed and passed then Push