Sig is solving it by reducing the weight of the trigger itself. Apparently, if dropped just so, the trigger can release the striker without being pressed. So, the fix is lighter parts to reduce the inertia in the trigger mechanism so that the striker won't be released by the impact in a fall. Sig is calling it a "voluntary upgrade".
https://www.gunsamerica.com/blog/sig-sauer-issuing-voluntary-upgrade-p320-pistols/
Interestingly, the P320 version that will be issued as the new Modular Handgun System isn't subject to this problem. The US Army insisted on a manual safety and that prevents this type of discharge.
I've held, and examined closely, but not fired, the P320. It's a very interesting pistol. The steel "chassis" has the serial number and all the fire control parts. Swap out different grip/frames and you get a different fit (a good feature if you're trying to accommodate the various hand sizes of over a million soldiers). The trigger feel was good (though, again, I've not fired it) and I greatly prefer it to the DA/SA of the M11 or M9 service pistols. I've qualified many times with both of those weapons (getting a 239 out of a possible 240 on my first time with the M11, which is a fine weapon) and while I'm used to this type of action, that 12+ lb pull on the first round is a PITA and detrimental to accuracy. I think that all of our service folks will benefit from the better trigger on this MHS/P320 pistol.
I liked the P320 enough to consider buying one. The modular nature makes it very versatile - change up the grip size or capacity for different shooters or uses. I was able to swap out the chassis very easily. It's a field-strip with one extra step and you've got the "action" in your hand. You could, with a bit of practice, swap out frames in less than 30 seconds.