The problem: The horse executes a sliding stop but anticipates and initiates a rollback, which results in a downgraded maneuver score or even a zero score.
Why does this problem happen? If the horse rolls back after a stop without being asked once, I can attribute it to mental error. If he makes a habit of anticipating a rollback after a stop, it's time to correct the problem.
Note: A horse can catch a rider by surprise with an uncalled-for rollback. It's happened to me! Sometimes that happens because the rider has schooled stop/rollback too much just prior to the performance.
How to correct this problem: I do not want my horse to ever anticipate a rollback. From the beginning I train my horse to wait for me to ask – whatever the next maneuver is. That way I am always in control. I do not "practice" rollbacks much either. He knows all the parts anyway and if he is responding only to my requests, he will have no difficulty executing pretty rollbacks in the pen.
Exercise: If my horse is a little too anxious to roll back after I stop him, I school him like this: Anywhere in the arena (up and down the arena or diagonal), I run him down and stop him. After he stops, I don’t release my body aid. That tells him to be prepared for something else and that he should wait to hear what I want! (My hands will clear that up for him.) I might back him up and then rollback either left or right (not necessarily the direction my horse thinks it will be). Then I switch it up – lots! Sometimes I stop, back up and rollback to right: sometimes I stop, back up and rollback to the left; sometimes I stop, hesitate a long time, rollback; sometimes I stop back up and relax; sometimes I just stop and rest.
Note: Stop/back up/rollback is never included in a pattern but that doesn't matter – this is about schooling my horse to wait to be asked. Backing up before a rollback (in schooling) gives me a chance to align his body if it is not aligned in the stop as well. I can make sure everything is correct before I ask for a rollback.
My horses pick this up very fast. When they do, it's a great feeling – almost a game – mixing it up and feeling my horse waiting for my signal for the next maneuver after the stop.