Hi,
"The KM is controlling 2 Slipstreams 120mm"
There is your cause. My channel 2 did the same thing and I also had 2 fans connected to it (parallel).
Scythe doesn't recommend connect more than 1 fan per channel because of controller overheating/damage. You will find out that the four capacitors next to the fan connections are getting VERY hot... some 80+ degrees. Maybe a 40mm fan connected to the case and blowing right at these capacitors will solve the overheating issue a bit.
I tried other potio's on mine but it never solved the problem; so the controller to that channel is damaged, not the potentiometer.
I'm going to buy the kazemaster ACE unit and replace the two 92mm fans for a single 140mm fan (VGA cooling).
Porto