Never heard and never had non rebuildable nozzle holders unless they broke, e.g, broken barb nipple, threads gouged up, or lower half of the body had a hair line crack so you had leaks in the middle. The intermediate disc can be "lapped" which just means a super fine sanding which is about the same as polishing. If you see rings like a bullseye, it's done for. In over 1,000s of injectors, I've only seen 2 broken springs. Otherwise, I suspect they can be rebuilt over and over.

How long did you let them break in? It takes 200 to 500 miles to get rid of the 'chatter'