Stabilitrak light, engine powers down car wont go above 25 mph.

Hello, we can try to guess at solutions here, but your dealer is the best place for your in-warranty diagnosis and repair. Definitely press them for a more permanent resolution, and contact General Motors perhaps directly for assistance. They may have a dispute settlement board in place for vehicles that have multiple unsuccessful repair attempts, and you may have recourse to at least put pressure on them for a permanent resolution.