Hi everyone, I'm having the exact same problem here.
I have 6 fans, 2 LL120 (bottom), 2LL140 (front) and 2 ML120 (top) that came with the Corsair Elite Capellix H100i white version.
Sometimes I notice that one of the bottom fans turn on a couple leds, and I am not able to turn them off, it's strange because all the other leds of this particular "broken" fan are customizable, but the ones that turned on for themselves aren't.
I already change the position at Commander but don't solve the problem, the only thing that solve this is turning off and then turn on the PC itself