Why do textures turn into blurry blocks in Ghost of Tsushima forests?

While galloping through the red leaf forests, the detailed ground textures suddenly turned into blurry blocks, ruining the visuals. I tried lowering the texture quality in game settings, but the game looked like it was from ten years ago, which was unacceptable. I used the GamePP Resource Scheduler to switch the I/O mode to Performance Priority and locked the power state. RTSS showed that texture-related frame drops decreased from 20fps to 2-3fps, and SSD temperatures remained at 45-52℃ per GamePP Hardware Sensor with read latency at 22-55ms.