i think i know the problem! this used to happen to me too in my 2022 Model S. I realized that if I opened the liftgate before I opened the door to get out, and then closed the liftgate, the screen and audio would still stay on inside the car. I would then have to open and close the door to have everything turn off.
However, if I opened the front door BEFORE i opened the liftgate, then once I close the liftgate, everything would turn off as normal. Very weird bug