Why would my front axles be popping and clicking when I turn corners

My front axles (both sides) have been popping and clicking when I turn corners (even slowly), just the same way they did when they had to be replaced. They have been replaced 3 times under warranty. I also had the boots replaced. The parts were from an auto parts store that my mechanic used. They were not Subaru parts. It seems like there must be something other than the quality of parts. Of course, the Subaru parts department told me that it was the quality, but this is rediculous. The mechanic who replaced them said that he would not replace them again, which I understand. I asked him the 2nd and 3rd time what could be causing this, and he said that he had no idea. Surely would have noticed something when he changed them, but I asked and he had no feedback. Once I had to have it towed because it stopped going into gear, and felt like the transmission. It turned out that it was the axle, and the mechanic said that it fell apart in his hands when he took the wheel off. This car has been so much trouble. Is this common with Subarus? Please help!