When you say one of the fans, what are we talking about here?
What's the spec, and what fan is it?
I don't know what that spec is, so I don't know if we're talking about a case fan, or a CPU cooler fan. If a case fan I might have been surprised to see it turn off on idle. If it's one of the 2 fans on an AIO cooler, I'm not sure why 1 would stop and the other not. I can't really guess without knowing what's in the system. Maybe someone else will know
I don't know what that spec is, so I don't know if we're talking about a case fan, or a CPU cooler fan. If a case fan I might have been surprised to see it turn off on idle. If it's one of the 2 fans on an AIO cooler, I'm not sure why 1 would stop and the other not. I can't really guess without knowing what's in the system. Maybe someone else will know
Seems to be. I'd be tempted to follow the cable and see where it's plugged in, in case it's loose at all. If the connection looks sound, you could also use temperature and fan monitoring software to see under what circumstances the fan changes behaviour. Did you change your fan profiles at all from the default that the system shipped with?