I don't think it does in NCC's case, because according to NCC's website, they own 100% of most of their plants, except for Indonesia (who K-CC/Samyoung owns 10% of), Samyoung (whom they only own 33.4% of) and Marcon (whom they only own 20% of). I'm pretty sure NCC import most if not all their materials from Japan as well, and KDK Corp (Hitachi Electrolytic Foil Research Co. Ltd), their subsidiary which manufactures ultra-high purity anodic and cathodic aluminum foil (99.8-99.98%), is their source for all production of aluminum foil for capacitors. And according to UCC, they are completely autonomous regarding their materials (IE, all materials are produced in-house, essentially, except for the chemicals NCC use to create the electrolyte itself - those are sourced from Tomiyama Pure Chemicals).
As for why some may seem to fail less than others... I guess that depends upon several factors. One of which is the condition of the anodic dielectric. A faulty electrolytic composition cannot properly heal the dielectric (or provide enough oxygen to "wet" weak spots), so even if KZG and KZJ do measure good for ESR and capacitance, once a weak spot in the dielectric appears, it could cause a permanent short in any otherwise "good" capacitor. But if the dielectric's condition remains good, this may never happen. As the porous dielectric deteriorates in storage from the diffusion or penetration of ionic particles from the electrolyte, the issue is only exacerbated.
The other factor I can think of is the rate at which molecules of gaseous hydrogen escape by way of rubber seal diffusion. If it doesn't happen rapidly, there won't be enough vapor pressure to rupture the cans or cause a difference in appearance and they'll silently drift out-of-spec as the electrolyte vaporizes and the water electrolyzes. Of course heat will accelerate the diffusion rate or the rate of evaporation, and if the thermal gradient is high (the speed of the internal temperature rise, AKA high ripple current loads), that will significantly shorten the life of the cap.
KZE and KZN also appear not to fail at all.
The difference may be a crucial stabilizer/getter that was omitted in KZG/KZJ, or conversely, some trace contaminant in KZG/KZJ that is not present in KZE/KZN.
But I guess when you're producing thousand of series and hundreds of millions of capacitors per month (billions per year), only so much can be done. KZG/KZJ and all ultra-low-Z variants from NCC were discontinued a while back anyway, completely usurped by their NPCAP conductive functional polymer line.
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