I'm a little confused by a couple points. Your last post lists four fans connected to mobo headers. I had assumed that BOTH of the two LED fans in the front were connected to the case's built-in manual fan control system, and that left THREE fans - two top and one rear - plugged into mobo headers.
Other item, please confirm. You have ONE fan that keeps changing, right? And you say it happens no matter where you plug it in, right? To be clear, it is that one fan ONLY that does this, it's not whatever fan is plugged into a particular header, right? If that is the case, that fan itself has a fault. It might be internal which means the only solution is replacement. If it was part of the case, contact the maker for warranty replacement. It MIGHT be a poor connection inside the connector at the end of its wires, or it MIGHT be that the springy metal part inside the connector is not making good tight contact with the pins of the mobo header. If you are "handy" with fixing such things you might investigate those. I would concentrate on the wiring for Pin #3 at the connector. With 3-pin fans, the color code usually is Black on Pin #1, Red on Pin @3, and Yellow on Pin #3. That Yellow wire brings a speed signal from the motor back to the mobo header. If it makes poor contact that keeps changing, the speed signals the mobo receives will be very noisy and unpredictable, resulting in speed readings that fluctuate wildly as you describe. NOTE that, if you observe the actual fan operation, it probably is NOT changing all the time if the problem is simply bad signal. But it might actually change frequently. If the mobo header thinks that the failure of the fans' speed signal indicates it has stalled, it will feed a full-speed signal to that fan to try to re-start it.
There is another possibility to check. In BIOS Setup where you configure each of the mobo fan headers, there probably is for EACH header a setting for the minimum speed of the fan. Unless you have changed those settings, all headers probably still are set the same way. If it happens that one particular fan is a little stiff, it might stall when the header sends out a minimum speed signal, and that might force the header to re-start it with a full-speed signal. So, try this. Go to the one header that feeds that troubled fan. Set its minimum speed a bit higher than the current value - say, for example, increase it from 200 to 350. Observe whether that makes any difference.
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