please help ib-m208p not working correctly!!!

Hi can anyone pls help, i have the ib-m208p running of my 2kxl to an alesis multimix 16, when i send any sound through the outputs 5/6 no sound comes into mixer (i have tried different sources to same mixer channel and it works fine) then if i change it to 7/8 it then comes through 5/6 and 7/8! i know that sound crazy but its happening! and driving me crazy! any ideas? im running os 1.14 which i believe is the most up to date, cheers