Assuming these are brass nipples, have the mechanic drop a drop of Tri-Flow down the barrel side of each nipple, and then try bracing each spoke using a "Twist-Resist" tool while working the spoke wrench to free the nipples.
...if they're alloy, I'm usually find myself calling for a nipple sacrifice while salvaging the spokes if they are quality spokes like DT, Wheelsmith or Sapim.
=8-)
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5000+ wheels built since 1984...
Disclaimer:
1. I do not claim to be an expert in bicycle mechanics despite my experience.
2. I like anyone will comment in other areas.
3. I do not own the preexisting concepts of DISH and ERD.
4. I will provide information as I always have to others that I believe will help them protect themselves from unscrupulous mechanics.
5. My all time favorite book is:
Kahane, Howard. Logic and Contemporary Rhetoric: The Use of Reason in Everyday Life