you may want to try this to reset your computer network. then reinstall netCut
Type ipconfig /release and press Enter.
Type ipconfig /flushdns and press Enter.
Type ipconfig /renew and press Enter. (this will stall for a moment)
Type netsh int ip reset and press Enter. (don’t restart yet)
Type netsh winsock reset and press Enter.
maybe you can try to install a VM windows , and try netCut inside VM.
in your current windows. do you have app, that allow your modify/view/queue/proxy network traffic between your PC to other service? that could stop netCut working on speed control.