|Sig P320 Compact (Source)|
And, as what some are interpreting as a mea culpa, Sig Sauer is already offering to upgrade pistols to correct the problem, suggesting that it has known of the problem at least long enough to come up with a solution.
So, why hasn't this problem surfaced earlier? Well, maybe it has. There has just been a lawsuit filed a police officer who claims that, in January 2017, he was shot in the leg when he dropped a P320 in a holster, and it went off. I suppose it is possible that the lawsuit was quickly cobbled together and filed since the reports of the problem first surfaced a week ago, but it is unlikely. (You can see a copy of the Complaint here). The Complaint lists a variety of other incidents involving Sig pistols discharging when dropped, but it is not clear if these are P320s or some other model. It also indicates that the Stamford, Connecticut, Police Department has withdrawn the P320 from service.
I would note that it doesn't appear that the accidental discharge problem affects all P320 models. The discharge apparently is due to the inertia of the trigger upon impact being enough to move the striker block out of the way, opening the path to the striker being able fire.
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Update: Added link to article on the mechanics of what is happening, and adding/altering the text to match. Corrected typo.