Torn Mounting Holes?
In Post #813, I perceive that we are looking at the half of the tank restraint which is normally behind the tank and closest to the pressure hull. It appears that the bolt holes, to which the strap which encircles the tank is fastened, have been torn out.
If the strap had not been adequately tightened, over time those bolt holes would have elongated and eventually failed, allowing the tank to lean out of it's proper position. This might then possibly have allowed the valve body to strike something firm and break off.
Of course, those bolt holes could have been torn out by some other mechanism.