I don't think Painted Ordnance necessarily produces a higher percentage of lemons than other gun makers, but when they produce one that is screwed up, it's usually screwed all the way up. A friend liked to joke that they must save up all their defective parts over the course of the week and assemble them into 100% defective guns on Friday.
That being said, my P-12 was 100% satisfactory, and my landlord has never had a hiccup from his P-12. Give the gun a thorough going over before you buy it, and you should be happy.