If hearsay carries any weight at all, I did speak to a guy who spoke to a guy in Germany who services and disposes of them.
He said that he said that he's never had one yet that failed when the handle was pulled - even many years out of date. Both rocket and 'chute.
So ... for what it's worth. It gave me a little comfort.
But, in any case, as has been discussed here before, anyone who has one might be better off firing it off sooner rather than later, when pressed by fate.
(Maybe after a bit of manoeuvring towards some nice-ish looking drop zone.)
If you pull early and it's a total fizzer, you could still have time to set up a conventional forced arrival.
Also, pulling and being done with it, means you're no longer carrying dangerous cargo and you have time to call mother.
And explain to your erstwhile friend beside you that ... well, these things happen.
What's the point of being the hero who gets it into the football field in the conventional manner but then shoots the sheriff who comes to help. ;- )