The IDF followed up their original statement, saying that the system was calibrated at a very sensitive level before the accidental launch and that the high-trajectory of the gunfire was identified by the system as a threat.
General Zvika Haimovich told reporters on Monday the following:
It's true that Hamas is actively trying to learn how to game the Iron Dome system, but the explanation still seems a bit odd, and it isn't clear exactly what he meant when he said some of Hamas's weapons are standard and some not. It's possible that some other reason was at least partially to blame for the incident, although openly discussing it could give away vulnerabilities with the Iron Dome system.
Regardless of what exactly set the system off in this case, the videos show just how insanely maneuverable the Tamir interceptor is. Some almost unbelievable snap turns can be seen as the missiles burn off their kinetic energy after their rocket motors burn out.
Each of Israel's Iron Dome batteries consists of a radar system, a few launchers containing 20 Tamir interceptors each, and a battle management and control unit. The 200 pound interceptor carries a 24 pound warhead that is detonated via a radial laser proximity fuse. Range is highly dependent on the target's flight profile but it's listed as between roughly two and a half and 40 miles.
It is widely noted that Iron Dome touts a success rate of 90 percent, but that number is based on projectiles it chooses to engage and usually at least two interceptors are fired at each target. Still, the system has proven to be remarkable in its capability and reliability which is what makes this incident so odd.
In a bizarre coincidence, the misfiring of the Iron Dome battery in Israel occurred while Saudi Arabian Patriot missiles were attempting to intercept ballistic missiles fired from Yemen. Some of the Patriots malfunctioned spectacularly during that incident, resulting in even more dramatic video.