leak theory
Plenty of oxy systems leak.Never seen bottle explode (until now maybe) If there was no sign of fire it sounds like a rupture/mech cylinder failure.
Blown the reg out of the end of it or a cracked cylinder serhaps?
I've avoided endless speculation but given they've found bits and pieces it seems pretty clear, it just remains as to why.
If a leak is noted ie more px drop than what would be expected or a history of too regular top ups it must be investigated.
There are no allowable leaks that I am aware of.
Sure gas escapes over time, it must, but real leaks are no go.
I'd say that 98% or more of leaks are the lines, joins, and charge fittings an maybe 2% or less regulator on the bottle.Never seen a leaky bottle ever.Just my experience speaking, others may have differing view.
Testing around 5 years hydrostatic that is depending if regulator or hydro date expires first.Not sure what internal inspections are carried out or if cylinders are x-rayed or other NDT carried out.
I have seen oxy bottles rejected for fitment by LAME's due to scratching or scores in the cylinder wall ex stores.
The cylinder in question may have been dropped or knocked hard to precipitate a failure long term.Not necessarily in service either.Transport, stores, overhaul are all possible areas.
I just hope there are enough clues not at the bottom of the sea to get a grip on the cause.