Accelerator Pedal Sensor problems of the 2014 Hyundai Santa Fe

Car was in park at take out window, when I put the car in drive and took my foot off the brake, the car lunged forward without my pressing down on the gas pedal. The car was hard to control. I was able to pull it over and stop, when I did the engine light came on. I shut it off, waited a few minutes, started it up, drove around the parking lot slowly and it seemed to be back to normal. The engine light stayed on for 2 days while it was parked in my yard, not using it. I drove it to my automotive shop to be looked at and while driving there, the light went out. They did a diagnostic on it and found the accelerator pedal position sensor was out and suggested the whole pedal assembly be replaced. They said it was an intermittent problem and would happen again. I had it towed to a Hyundai dealership as it was under warranty. I was told they could not find what was wrong and tried to return the car to me without fixing it. I have refused to pick it up until it is fixed to prevent a future accident or injuring someone. This is a major safety issue that needs to be resolved. The car was dropped off on 2/25/19 and they still have it today on 3/6/19, with no communication from them since 3/1/19 when they told me to come and get it.