Going back to nozzle failures earlier in the thread: That looks like a brittle failure, rather than an overstressed failure, judging* by the shell-shaped tide marks in the failure face on the pictures shown.
This is an injection moulded part- Understand that an injection mould will have 3-50 part spaces in each tool, so a single 'shot' produces as many as possible.
It's most likely that there are 10 or so nozzles in each shot. If the tool is poorly designed and/or process controls aren't being adhered to, you often get the part-mould furthest from the shot being poorly cast- The pla