Why does Need for Speed FPS drop from 60 to 30 on Onda H610M+?

I've had enough—every time I hit the high-speed track, my FPS would drop from 60 to 30, which is a disaster for racing. I first tried lowering CPU voltage in the BIOS to reduce heat, but while temps dropped, the frequency became even more unstable and stutters worsened. I then used the GamePP Power Plan Switcher to lock High Performance mode and locked the VRM fan to 1500RPM. HWiNFO64 showed the frequency range converged to 3.8-4.1GHz and fan speeds stayed at 1400-1600RPM.