The P320 absolutely has design and manufacturing flaws. The P250 fire control unit was shoehorned into a striker fired pistol when they should've gone back to the drawing board like they did with the P365, which doesn't have these issues.
There are also manufacturing issues with intermingling parts with different geometries intended for different calibers and building guns with the wrong parts, such as installing a 10mm Auto/.45 ACP takedown safety level in a 9mm gun, or installing a metal injection molded firing pin safety that's out of spec, worn, or contributes to tolerance stacking in such a way that the gun becomes unsafe.
These are all good theories. Someone should demonstrate it if true. When there were drop safe questions, it was able to be reproduced, and there was a change to address it. Show an uncommanded discharge, show why it happened. Then you have a design or manufacturing flaw.
I think the problem is that there's not a single identifiable problem. There's a series of related problems caused by manufacturing and engineering decisions that lead to parts not interoperating as designed.
For example, Sig offered a "voluntary upgrade" to fix the well documented drop safety flaw with the P320, and there's video proof of the same guns going off still in holsters.
Sig is going to be playing whackamole fixing these issues if they ever admit to it, so they won't.
It really doesn’t matter at this point whether someone is able to document it or not. There is a lot of anecdotal evidence of uncommanded discharge (yes the plural of anecdote is not data), and the reputational damage to the gun and the brand has already happened. If I were in the market for another handgun at this point, I would personally skip the Sig, because even at a %0.001 chance that this is a legit problem, my risk tolerance around firearms is pretty low, so I’ll just spend more and get a Glock where I’m certain it’s safe.
There are also manufacturing issues with intermingling parts with different geometries intended for different calibers and building guns with the wrong parts, such as installing a 10mm Auto/.45 ACP takedown safety level in a 9mm gun, or installing a metal injection molded firing pin safety that's out of spec, worn, or contributes to tolerance stacking in such a way that the gun becomes unsafe.