I'm not gung-ho about people solving problems by stepping away from the problem, but this may be the best option to avoid the muscle memory of bad shot mechanics.
This makes me wonder about Painter's coaching style and the "telling them straight" mantra. Players need to be mentally tough, but they're family once they come into the program and figuring out how to help them also has to be a consideration.
Treed, my apologies. Damned if I know what it's like to watch your child struggle, but it's clear that something has hurt his confidence in his shot and developed that hitch.