Okay, I took another look at this, and to no ones surprise, this is more complicated than it looks.
For some reason they chose to use "nitrocarburized steel" rather than heat treated, high carbon steel, like the rest of the world does.
Carburization puts a tough outside skin on a soft, low carbon substrate.
This process is used extensively in the firearms industry, Glock does it's barrels this way. It allows for a hard surface over a much softer base material. This is for wear resistance and resistance to fracturing or splitting.
Apparently the carburization does not travel well, up the filament orifice, so it stays soft, with no hard skin over it.
Whatever amount of these nozzles that they pre-made can not be annealed and re-hardend.
Their only choice is to re-make them all out of high carbon steel, and heat treat them properly.