Preventing a paradox

In the future this Jon had accidentally changed his gender, and then used a time travel wish to negate it causing the timeline to start to unravel, so She returned in time to switch stones to hopefully save time. With that she left taking the original stone with her. The stone she left was the same wishing stone but modified left by a 23 year-old female Jon. It would work like the regular stone but would force Jon to wish himself into 19 year old coed with Karyn and not to try and restore her male hood or age.