The yellowish film sounds like a conformal coating that is peeling off. The circuit does look similar to the 3 I have, although I have the old beige Russian boards with the traces that lift off if you are too aggressive with them. They are great mics. The two I got from the now defunct Sound Room are outstanding, I bought a GC special on eBay as a test bed for modding. It’s on my list of things to do as this point. The capsule on that one isn’t of the same caliber and will be replaced.
If it were me and they fit the good Russian capsules (you could ask someone who works/worked on these a lot, like a Michael Joly (no longer modding, but a wealth of info) or a Bill Sitler,, who wants to sell mod kits), the first thing I would do is take the PCB and try to clean up the high Z portion with isopropanol, flux remover, etc to see if it makes any difference. If it is the same circuit, AND the legit capsules fit (the matched pair Russian ones I have are great), then you can consider replacing parts.
Is the mic preamp noisy without the capsule? You may have to put a small cap (e.g., 50 pF) between the FET gate and ground to properly test that. I don’t know the capacitance of a real 102 capsule.
My only concern is that the mechanical quality of the Chinese hardware. Even if they fit, if there is not good electromechanical contact between the capsule and body, it will be a frustrating experience. Just my opinion.
If you didn’t get what you paid for and are not in this for the long haul, you may just want to start over with the real thing