A couple of years ago, a friend with a brand new Sako 85 had a round go off while stalking in the Highlands. On to a hind, he slipped the safety for the shot and the round fired before he touched the trigger.
To this point the rifle had performed faultlessly. He chambered another round as the hind, not hit, hadn't moved far.
As he closed the bolt.....gently, again the round fired without him touching the trigger.
He didn't attempt to use the rifle again on that trip and took it stright into the dealer on his return home. But, we noticed testing it back at the lodge, once cocked, provided the firing pin didn't inadvertently go off, the action of sliding the safety catch to 'Safe' was enough to dry fire the rifle. If the safety made it to 'Safe' without firing, then releasing it from safe to fire would once again dry fire the rifle. It was a matter of luck, so the rifle was deemed unsafe at that time.
The dealer in front of my friend & I removed the steel from the synth. stock. It was immediately apparent a hex. bolt holding the trigger assembly in place was significantly loose. Once tightened, the rifle functioned perfectly in all aspects once more.
What's astonishing is that if something of this nature fails, the rifle should be able to discharge at all.
Naturally, we all know about muzzle awareness and follow usual safety procedures when handling firearms, nevertheless, I should have imagined it not beyond the wit of man to redesign the trigger/action so that in the event of a failure of this nature, no discharge could occur