Fuel Delivery problems of the 2007 Nissan Sentra

My son bought a 2007 Nissan Sentra s on July 27, 2007. This vehicle has broke down on 08/03/07, 08/07/07, 08/10/00 and as of today it is still at a Nissan dealer. The problem with this vehicle is that three times the while driving along for no reason it the car speed drops to 5 mph. The first time it happened was at development and no other traffic. When this happened the car would only go 5 mph. No faster. The second time this happened my son had two clients in the car and was able to get off the highway. The third time this happened my son and I were returning home. We were traveling up a two lane road with many vehicles going both ways, as we got half way up the hill this happened again. We had no place to pull off and almost go hit from behind. Thank god the driver was able to get around us. We had to put the 4 ways on and was only able to go 5 mph to the top of the hill. Still with no place to pull off the road I told my son to drift the car down the hill into our home town. My son drives this car on interstate highways every day to go to work if this happens on that highway while everyone is going 65 mph he is not going to time to get off the road. I have contacted Nissan and complained and they told me they will fix the problem that was the second time it broke down. I fell this car is unsafe to be on any highway.