Which sgminer you're using? Does it support Xevan algorithm?
I use sgminer-xevan-5.5.0-nicehash-1-windows-amd64 and also had a problem, now I solved it by playing with intensity, just for ex. -I16 . I can't tell you more 'coz I mine on another pool. Hope it will help.
Also note for example for my HD7850 'xevan-mod' kernel doesn't work. I use 'xevan' instead