Your cable is getting stuck when it is turning in the outter cover. The same thing was happening to mine, put a new cable on and it sortted it.........for 2 weeks then it went again.
yu know wot i meant! see if yu can route the cable so that it is as straight!! as possible - the tighter the bends or any kinks will screw it fur sure.
All three of mine had this problem. the noise thing is still there at higher speeds you just can't hear it above the reassuring rising cacophony of mechanical sounds. I love it! It takes about two minutes in the 90 to forget all about the Hippo. The thing is a 90 has noises that are supposed to be there, Hippos have noises that induce paranoia.