Looks like that area of the case was not supported by the chamber. Like said above, out of battery.
I believe the group has sorted out the need for a cartridge gauge, which can detect cartridge construction errors. But we should get back to the "
Why ?" of the matter.
9x19 Luger belongs to a very small, select group of cartridges, and as such constitute a special situation not found in most other handgun cartridges. The root cause is that the 9x19 Luger cartridge is
not a "straight wall case", it is a
tapered cartridge case. It's that
taper that can allow bad things to happen more often; bad things that don't usually show up with other common American cartridges.
Suppose you have a cartridge flaw in 38Spcl, 38Super, 40S&W or 45ACP. As shown below, the chamber will not begin to accept a cartridge with common issues (say for instance incorrect taper crimp)...
Compare that to the tapered chamber of the 9x19 Luger. The 9mm's
tapered chamber actually makes the problem worse by allowing a faulty cartridge to enter. In this way common issues, such as incomplete taper crimp or blown out case head diameter, can
partially enter the gun's chamber and then allow the gun to fire in an out-of-battery condition...
Therefore 9x19 Luger needs to include extra quality checks to scan the exterior of the finished cartridge.
It's not "harder" to reload 9mm, it simply requires more process steps in order to obtain the same level of safety found in other cartridges.
Hope this helps.