I have two miners running Win10 as well.  This happens for me when the AMD driver crashes on a particular card.  I will get the error from AMD and when I look it may have 1 or 3 cards that are mining at zero.

When this happens I have to fully shut down the miner, bring it back up and then I can use it again.  A reboot will not work in this case.  (it appears to hold on to the problem - as if it requires the video card to lose/drain all power)

I have a separate box running LinuxMint - trying to see if I can't run it the same, but it doesn't have (or I haven't found yet) the same way to boost the cards as I do in Windows.