2024 Hyundai Sonata VEHICLE SPEED CONTROL

The vehicle speedometer is occasionally 5mph off. When I first get into the vehicle after it’s been sitting for a while and drive around, the speedometer works perfectly. If I shut the vehicle off while getting gas, running an errand or something similar that involves the vehicle sitting for a semi-short period of time, the speedometer will be 5mph off when driving. I initially detected this issue be noticing that my speedometer was different from the speed posted on a GPS based speedometer on my phone, who’s speed exactly matched those road side speed measuring signs found on the highway, but both of those measuring devices differed from my vehicles speedometer. I brought my vehicle into my local Hyundai dealership who verified the problem exists, but mentioned that this was a software issue which needs to be corrected my Hyundai Corporate. I contacted Hyundai Corporate at the number provided to my by the dealership, and was essentially told that there is nothing they are willing to do to fix the issue.

As I’m driving 75 MPH, my car slows down and on the dash board it reads 20 MPH LIMIT. I’m on the Expressway and, prayerfully, by putting on my HAZARD BLINKERS, I pull over, wherever it’s safe, turn car off, restart the car and then it’s fine. PLEASE HELP BECAUSE THIS IS A LIFE THREATENING SITUATION! SCARED This has occurred SEVERAL TIMES.. Approximately 1 month ago I took it into SERVICE DEPARTMENT (kept 1 week and never slowed down on them. Again, once the car is turned off, it drives fine. How can I turn off this 20 mph hour limit on dashboard. Any advice or help you can give me to put me at ease, is CRITICAL! Thank You in Advance.