2014 Taurus Steering Rack Failure

Fourth rack has failed in 7k miles. Good alignments after previous rack replacements. Replaced all suspension components. It is an internal failure not Rack module failure. What can cause premature internal rack failure? Is this a low workmanship issue? Original rack wasn’t as bad as these. What causes rack failure if it might not be workmanship? Ford dealership confirmed rack was installed properly by me, they confirmed internal failure, they confirmed all other suspension components were installed correctly, confirmed toe keeps going out, confirmed alignment was done correctly, and programming is correct. They did not mention anything about poor workmanship or cause.