2011 Hyundai Sonata Hybrid intermittent acceleration problems

Hi
My 2011 Sonata Hybrid has been have acceleration problems intermittently. Years have gone by, the car has been in three times each time they tell me they can’t duplicate the problem. It also has a intermittent surge forward during braking which I feel is connected to the acceleration issue. You probably know it is drive by wire and uses a Throttle Position Sensor. My thought is the TPS system is getting a bad signal to both. the computer therefore is confused and won’t accelerate and during braking tries to accelerate. Both these issues are a serious Safety concern. I am now able to enter traffic correctly and I will at some point hit another vehicle because of the braking surge. I think it is the TPS . I have not had a check engine light. Hyundai says they can’t fix it. All they have done is drive it to get the issue to happen. No further investigating has been done on their part. refusing to try to diagnose the issue in any other way. If the computer can’t find a problem their so called techs are dumbfounded. How can you help me ?