The stock fan that came with the cooler always stops spinning, randomly. Strangely, it "tries" to spin, but then stops for a few seconds, and repeats, as if it is struggling to rotate. I would have to give it a spin boost with my finger to get it going. Sometimes it just works as it should. It is plugged into the motherboard (CPU Fan 4-pin). Can anybody give me some insight as to how to fix this, without having to connect directly to the PSU? Could this be a MOBO or BIOS issue?