I’ve been trying to record my semi acoustic guitar into cubase and when I play the audio back it sounds like its phasing or flangeing, like there’s 2 tracks playing the same audio (there isnt) please can any one help, im using the scarlet 2i2, ive tried various buffer sizes, disabled control room, and played about with the Asio guard and the steinberg power scheme 
First you need to determine if the phasing is being caused by something within Cubase or is it part of the audio recording itself. Use a standalone audio player to listen to the recorded file. Does it sound phased?
My guess is that you recorded the audio using 2 mics or a DI & a mic and it has introduced some phase alignment problems in the recording.
Hi thanks for your reply my guitar is semi acoustic and plugged directly into the focusrite scarlett 2i2