Why does Judgment drop from 90 to 40 FPS in crowded areas?

Walking through Kamurocho, whenever NPC density increased, my frame rate would plummet from 90 to 40 without warning. I tried enabling the XMP profile, but the system blue-screened twice, which made me very anxious. I used the GamePP BIOS Load-Line Voltage Adjustment Wizard to tighten timings to 36-38-38-72 and raised voltage from 1.1V to 1.25V. AIDA64 confirmed latency stabilized at 72-78ns, HWiNFO showed temps at 44-50℃, and MemTest86 passed 4 rounds with zero errors.