Could you describe in more detail what you mean by "randomly" i.e. are the surfaces jittering slightly or moving with large throws?

Which radio are you using? Did you set your radio to PPM mode? What type of adapter cable are you using? Did you push all the connectors completely in?

Did you perform a calibration of your radio in AFPD? If you're using high rates, you will need to calibrate with your radio set to high rates.