Looks like a common problem. I was affected too. Bought mine (also version I)  in 2009 as second hand (still payed 4600 Euro then).  Later had it serviced by Nikon and got a SWM motor replacement installed. Finally a few years ago after seeing very little use and thus resting for some month I detected that it could nearly not be focussed any more. After sending it to NikonGermany again I got the reply that it needed a new inner focusing helicoid but that is not availabe any more. Finally I got it back having lost the little remaining ability to be manually focussed.

The lens was a revolutionary internal supertele-zoom with constant maximum aperture when it came out (and little to none none of the manifold "non-Pro" supertele-Zooms were available then) had great close-up capability and performed well in low to medium ranges but was found out to be subpar at longer distances. I dont need it any more but I share the disappointment that an expensive lens like that cannot be brought into life any more. It is the only lens of many I own that became unusable.

Now the only one thing that disturbed me is the overcorrected spherical aberration. If you look at the small lights, you will see "O"s suggesting a mirror lens, just smaller. Here is the full shot and a 100% crop at f/2. I got as close as possible to the crow; ten centimeters closer it would have flown away.

Also, you get an idea of the vignetting.

Not so happy with the 23/1.2 (I'll resell it), I decided to buy the 35/2 and indeed it is a different animal. Not perfect, but... judge for yourself. All pics SOOC.

For one thing, it has near-zero distortion and very good overall sharpness.

Frank, a gorgeous portrait, no matter the convoluted technique used.
John and Arturo, two great shots and two very different painters, if you look at the background. The Rokkor (wide open I guess) uses a squirrel quill while the other one (which lens?) an airbrush.

We live indeed on different planets (?)

The conifers around here are unhappy about being weighted down by thick coats of frozen snow. I can understand their feelings.

I like that photo of the German-Jewish genius, his enigmatic and observant gaze.

I believe the language of the future is being formed; humanity still has to evolve. Sometimes I think we're almost primates.