What happens when you play a CD, wav or mp3 located on the PC, if they are also a problem then I'd be digging into PC sound path.
Have you tried another interface, take the laptop into the place where you were/are doing the audio course and they a couple of theirs.
Focusrite stuff has a pretty good reputation for reliability.
Still waking up and only halfway through the 1st coffee, I'll keep thinking on it