Fans won't shut off

Hopefully I can get some help with this. Problem is, when I shut down the pc my fans continue to run infinitely. Everything from the chassis, cpu, gpu, psu, optic drive. I've checked to make sure windows is set to shut down, I've looked in the bios settings. I've cleared the CMOS. I've updated the bios. I've tried a different PSU. I thought it might be the board, however this is the second board. First board was RMA'd due to a faulty ram slot and had the same issue.

The fans are all PWMs, 3 are connected to a chassis header via spliter. Cpu's are connected to the cpu header via spliter. However, one of my cpu fans will occasionally shut down, which seems strange.

Im wondering if it might be an OS issue. I might try reinstalling windows. Otherwise Im lost. I wouldn't think it'd be the board, not two in a row. At least I sure hope not.

Any Ideas are greatly welcomed.

Thanks

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