Why do textures flicker in Rainbow Six Siege with Kioxia EXCERIA PRO?

While sneaking into cover, walls would suddenly turn into low-res blocks, which is incredibly distracting. I tried lowering texture quality to Medium; the flickering stopped, but the game looked blurry and lost all detail. I ran the GamePP Peripheral Driver Conflict Detection Tool and disabled a conflicting USB controller service. Now, RivaTuner shows frame times stabilized at 9-13ms, HWiNFO confirms temps at 51-58℃, and CrystalDiskMark shows I/O wait times are down to 12-25ms.