I have a 2017 Tahoe Premier and have experienced the same thing ... This is my 5th or 6th Tahoe and the first one that has ever given me problems. At first I thought is was a rough engine issue, but am leaning more towards the trans issue that you described. I have also noticed that the "neutral drop" symptom seems to happen more often after the truck has been sitting for an hour or so??? Wondering if this is this a low trans fluid or pressure issue?
Have also been experiencing rather poor mileage on the road ... Averaged around 19 on a 2000 mile road trip to FL and my previous 2015 Tahoe would get 22-23 on the same trip. Have you noticed what I will call a "shudder" when slowly accelerating?
