Throttle Position Sensor going out repeatedly

My car's tps sensor keeps going bad. I just took it to the shop and was told it needs replacing- it was replaced by a different shop Nov of 12, a friend did it in Feb of 12, it was replaced also early 2011, before that 2009 and also in 2006. No one has been able to give me a reason it keeps going bad other than the last time it was replaced they said there was a broken wire, so they replaced the pigtail leading to it. Here I am less than a year later and it's going bad.
A friend did an oil change and a radiator flush two weeks ago on it and also sprayed a degreaser on the engine and hosed it down. I do have a small oil leak and a coolant leak. When I parked the car to do the oil change and radiator flush it had been running fine, no check engine light. When I started it after we were done, the check engine light was on. It still ran well- smoother actually than before. A little later it randomly shut off. It did it once again a few days later, then twice yesterday. Took it to a shop today and was told my tps sensor needed replacing and my egr sensor/valve needed replacing. The egr valve had also been replaced last Nov.
Any ideas on the root cause of this repeated failure? I'm not getting any answers from the shops.