The standard name for that tooth IS the pickup tooth.
It seems like the general consensus is an AoE issue. So how does damage like that happen without any sign of wear on the pickup tooth, 2nd tooth or release tooth? The release tooth looks perfectly fine, a release tooth failure results in stripping of the entire piston rack not just damage to the front few.
I've seen similar damage but to a much lesser extent on one of my Modify pistons. The gun still worked fine, but it was caused by a worn out bushing, so make sure your bushings are perfect.