Gas Recirculation Valve (egr Valve) problems of the 2018 Chevrolet Traverse

Began 6/19, with progressive worsening. When the vehicle is placed into park and shut-off, a warning appears on the info display stating" shift to park". At which point the vehicle keeps all lights on the inside and outside of the vehicle illuminated, the ac stays on, the radio/entertainment display stays on, in addition to a warning beep/chime that is typical when the vehicle is left "on" and you open the door. In other words, our vehicle still thinks it is "on" and "in" gear. In the beginning it would take 2-5 times of turning the vehicle back on and off in order for the warning to go away and the vehicle to shut-off properly. Now, it will no longer shut-off regardless of how many times the engine is restarted and the stick-shift is moved out of park & back. Have resorted to unplugging the battery every time we exit the vehicle to keep it from being drained. The vehicle has also not re-started at all(taking 15 minutes of re-engaging the starter button at its worst). Leaving my wife & toddlers stuck in 100plus degree heat. When it does not re-start, the dash display reads the vehicle at "0 mph" and allows the gears to be shifted. There are numerous other people online stating similar issues. Some have resolved with a change of the shifter mechanism, & others still with continued issues after that. The dealership stated there is only 1 part left in town, and that it is on back-order and they can't get it from the manufacturer(they tried their two nationwide warehouse locations). Not only that, the dealership said we needed to leave the vehicle with them and they would not even "look at it" for up to 1. 5 weeks, and that they were out of loaner vehicles. The vehicle is still under warranty, and was purchased certified-used. Nothing has occurred while driving the vehicle or when stopped at a light/stop-sign, but we certainly don't want to find out what "could" happen.