GM Dealer Made Huge Mistake! $500 Diagnosis & $3900 In Repairs!
I don't know if this could be part of the problem, but Eric O of South Main Auto fame recently had a guy bring in a newer GM vehicle with electrical problems, steering, trailer brake warnings, etc. ,,, including a
shift to park issue.
In this case, it turned out to be the main ground strap (braided) between the body and frame, which had gone green and crusty, and was in the process of disintegrating.
The guy had paid GM 500 bucks to tell him 3900 bucks worth of parts shot from a cannon would fix the electrical problems with his steering and such, but nothing about the shift to park thing.
Once Eric repaired the ground, all the electrical problems the guy had were fixed, including the shift to park issue.
I would dismiss a bad ground somewhere.
Jay