This does sound like a problem that should be looked at. However, you should try to get a video of it happening, since a problem that happens "sometimes" is hard to diagnose, and the mechanics might decide you are just crazy, or that they would rather charge you for an hour's diagnostic time and do nothing than charge Chevy for an hour's actual work (at the much lower warranty rate)
I am curious how you know it is even happening. It isn't often I take off the clutch and sit on a hill waiting for hill hold to click off... only when I am wanting to roll backwards and am too lazy to shift to reverse and make the car do it.