Yup, wacky display behavior etc. often accompanies 12V battery issues (bad battery, loose connections, etc.). A bad battery seems unusual on a new car, so my inclination would be loose or poor connections.
Whatever it is (did they give you error codes, details?) sounds like it's not a "normal" issue, but something rare. I'd prefer they think it through than just rush into something half cocked. That they have GM involved seems like a good thing, versus being a cowboy.i have to say, that the lack of info has me a bit Concerned