Neumann used the best resistors they could find when they built these mikes, but they do fail. Replacement with a cheap carbon resistor I find insulting to the heritage.
Yes, I find that strange also.
The first mic I built, I used this style of resistor, because up until then the only tube electronics projects I had done involved guitar amps, where old Allen-Bradley carbon composition resistors were rumored to add "something special," so I thought the same would be true in tube microphones.
I now know that to have been mostly misguided. But if Klaus says this one isn't hurting anything, I'd trust his expertise.