It seems the problem is not with the stocks, their design, or strength but more to do with the way someone decided to change making them without being instructed to. From what I can gather machinery has been used somewhere in the construction where it was supposed to be done by hand causing a weakness which presents itself on firing.
None of this was official so please dont quote me or Blackhawk but as far as can be gathered the item required careful torque applying by hand and not winding up with a machine so presumably something threaded was damaged. This obviously being in the grip area so to do with that main spring and the heavy tension its under.
Anyway I'm very impressed with the advice and help I've had from them so far so a big thumbs up in that department.
They are not saying by any means that all Mossberg stocks sold are affected but to be safe are taking them all back.
I guess someone(s) in the construction process now have rather sore behinds!.