One thing to try is to go to your Win10 devices and printers. Select your controller and right click on it to get to a calibrate mode. After this, try calibrating it in RC8 again. Also, some controllers do not have very good centering to begin with. Try adding 20-30% expo (in your Tx and / or RC8 advanced controller setup).
If there is a constant flight error maybe try editing the model to shift the CG accordingly (eg. If it has strong nose down, try moving the CG rearward. Good luck and cheers mate.
Edit; I find that my Spektrum Interlink DX controller work perfectly with RC8 and highly recommend it.