Why does Phantom Brigade drop to 45 FPS during parkour scenes on Great Wall GW3500 1TB?

The screen jittered on every landing in Phantom Brigade, dropping from 60 to 45 FPS. I tried lowering graphics quality, which stabilized FPS but ruined the visuals, causing anxiety. I used GamePP Power Plan Switcher to set High Performance mode and locked the CPU core voltage. GamePP Frame Time Analyzer showed frame times converging to 14-16ms, down from 16-22ms. CPU temperature remained stable at 72-78℃ per GamePP Hardware Sensor. The action is finally responsive.