Front Suspension Control Arm problems of the 2007 Lincoln MKX

Approximately 18 months ago, I had the lower control arm replaced on my vehicle, as it was found to be faulty and covered under warranty. When replaced, I was told that I should not experience any additional problems with it. Today, I took my car back to the dealership, and I was told that the control arm was faulty again and needs to replaced. This time, it's not covered under warranty. In reading many of the complaints about this particular model year, I notice that many people have had the same issue, which leads me to believe that there is a manufacturer defect in the parts being used.