What had happened is the shortest key pin is small enough to allow the driver to also enter the plug below the shear line, causing a lip that the spring caught on causing the damage seen and jamming the plug.
This picture is with both key and drivers in the plug - no key.
This wouldn't happen if the key is used, but it essentially makes the lock a 4 pin cylinder effecting the security. What it you had 2 or 3 high cuts in the biting???? 2 - 3 pin lock? Not a very good design. Is this common in other brands?
J