I would stay away from the "my skills were improving" because of this activitiy. That's not going to help you win. For example, a security officer's skills may well improve by participating in bank robberies. That doesn't mean that participating in bank robberies is a good thing for a security officer to do.
Your best chance on appeal is to present that the repair activities for your supervisors and for other employees in the company appeared to you to be both expected and appreciated. While being paid by the individuals for the work you performed was nice, your primary motivation was doing what appeared to be expected of you by those in control of your career in the company.

