I have one of this switches too - there is a known problem, with it and SwOS. Mikrotik is aware, and said it will be addressed in future releases.
I believe this thread will help You:
http://forum.mikrotik.com/t/high-rx-mac-errors-and-rx-fcs-errors-on-crs328-24p-4s-and-css326-24g-2s/123286/1
There is one solution: run RoS, instead of SwOS. I know, I know: disappointing. Yes, it is. But it’s better than not getting 10Gbps.