I have to figure that it is user error or bad sourcing, or both. I have seen a decent number of people use it with little trouble other than standard discomfort. The ones that were successful were very precise and modest in the dosing. Now I've seen people upping it little by little every year or doing things like laddering it.
I also wonder about sourcing now too? Back years ago, the stuff usually came through reputable chemical suppliers, now I wonder if it's much like steroids, where the lines have been blurred.