On April 23, 2024, while decelerating gently at a traffic light, I heard a loud thump sound from the rear of my 2021 Porsche Taycan. Immediately, the vehicle lost access to the Reverse (R) and Park (P) gears. I was able to slowly coast into a nearby parking lot, but then all gear positions (Drive, Reverse, Neutral, Park) became completely unresponsive. The vehicle was immobilized and had to be towed. At the time of failure, the vehicle had just under 45,000 miles and had received routine maintenance and a recall inspection at a Porsche Center in March 2024. The factory warranty expired only one day earlier, on April 22. Porsche is refusing to cover repairs or provide a loaner vehicle, even though the failure clearly occurred at extremely low mileage and immediately after warranty expiration. The failure pattern matches the symptoms described in TSB #2209 (NHTSA ID: 10210797) for the 2022 Taycan, which identifies a known defect where the vehicle unexpectedly shifts from D or R into N or P without driver input. While my vehicle is a 2021 model, the behavior is nearly identical ‘ sudden loss of drivability, unexpected gear disengagement, and major safety risk in traffic. This incident could have resulted in a serious accident had it happened in moving traffic. I am submitting this complaint in hopes that NHTSA will investigate whether this known transmission defect also affects 2021 Taycan models, and to ensure Porsche takes responsibility for latent safety defects, regardless of narrowly expired warranty status.