I am not a qualified armorer or even a graduate of SDI, but here's something I noticed.
The SIG P320 uses a sharply different striker block than most other pistols out there. Instead of a button, it includes a little swinger that is very narrow. It can get damaged if officers drop the slide while cleaning. I know, it's a pretty remote possibility, but it can be jammed into the slide. Well, same can happen to a traditional button, but it's less likely because a button is this much sturdier and the friction surface goes around a cylinder.
In addition, the striker safety lever on P320 is co-located with the sear. I see an opportunity for the sear affecting the safety lever, or vise-versa (although they do not sit on the same pin). All you need to have is a little piece of foreign matter working its way in. On most other striker firing pistols, such as Glocks, these mechanical elements are far apart and the mechanical connection between them is highly unlikely. Specifically on the Glock the connector cannot pull on the cruciform and thus the transfer bar, only push, so its failure cannot disengage the striker safety.
And one other thing, on a Glock the striker is not fully cocked, but on P320 it is. Of course that is only comforting if primers are hard enough to make a difference.
This case also brings up to mind a member of these forums who had an SCCY CPX-2 go off on its own in his house. The notable part about the story is that CPX-2 is a full DAO gun, and its hammer is never cocked. The poor guy maintained his innocence and the general opinion ended being that either his child or his wife fired the gun, but didn't own to it. But some of the most ridiculous theories were floated in order to explain how it could happen, mechanically speaking.
Likewise, it's most likely that officers were not entirely honest here. But nonetheless, P320 has a uniquely intricate mechanism with some rather obvious weak spots.