Does stuttering in the second tasleem of prayer and correcting it after a pause invalidate the prayer?

Stuttering is beyond a person's will and is excused. Your prayer is valid and not invalidated by stuttering. The second Tasleem (salutation) is sunnah, and the prayer is valid with one Tasleem. It is important to note that stuttering is sometimes a symptom of obsessive-compulsive disorder (waswasah).