Why does Metro Awakening freeze when entering underground tunnels?

Entering gloomy tunnels was torturous; the loading screen would hang at 88% for seconds. I tried running a disk defragmentation, which is useless for NVMe drives and actually slowed down response times, leaving me feeling helpless. I accessed GamePP NVMe Queue Depth Configuration, increased depth to 128, and optimized the write cache. CrystalDiskMark showed random reads rising to 56-64MB/s, HWiNFO confirmed temps between 38-47℃, and an internal timer showed loading times drop from 14s to 7s.