I fixed it!
I got sick of it happening and opened it up to see what I could see. It turns out the ribbon cable connecting the two boards had been folded and had a nasty kink in it. It didn't seem to be damaged, but I replaced it with a new cable anyway. I also checked for dry solder joints and used compressed air to blow out a tiny bit of dust ect.
Reassembled it, and it's been perfect ever since. I don't recomend taking it apart as it probably voids the warranty. My unit was second hand, so I just went ahead and did it (with an antistatic mat) and all is well!
