Why does Banishers drop from 240 to 120 FPS on Onda H610M+?

Aiming was impossible in Banishers due to 240 to 120 FPS drops. I lowered shadow quality, but it ruined the visuals. I used GamePP Resource Scheduler to set real-time priority and optimized drivers. RTSS confirmed frame time stabilized from 4-15ms to 3-4ms. VRAM usage stayed at 85-92% per GamePP sensors, setting a smooth baseline.