Why does Far Cry 6 drop from 70 to 35 FPS during jungle stealth missions?

My stealth flow was ruined when the frame rate plummeted from 70 to 35 FPS during jungle combat. I tried manually locking core frequencies in the BIOS, but that just caused memory checksum errors during boot. I then used the GamePP Resource Scheduler to set the priority to Realtime and bound rendering threads to high-performance cores. Frame times converged to 13-18ms per GamePP, CPU temps hit 68-74℃ per HWMonitor, and GPU temps stayed 60-78℃ per GamePP.