Wow. Never saw a broken Core before now! I know broken Cores exist, but they are built like tanks!
Probably just metal fatigue on a weak spot in the metal stock used that day of production.
Hopefully they'll have the part. I like the Core more than the SuperTool 300. Core has finer HD pliers and no tool clumping
But, if they don't have the part, a new ST300 should take the sting out of the Core lock breaking.