[Speedslug]

I am not familiar with enough torches to comment on 'faulty valves' from the factory but I have learned from others that the mating parts in torches, regulators and tank valves (oxygen and fuel) are made from extremely soft metal and that over tightening, even by hand, kills them in just one or two closings.

Also, any dust getting into the lines or carbon residue from back flash flames 'popping' backward through the torch has enough grit to scratch the mating faces and allow leaks to develop.