brother 260 knitting machine?

My bro 260 knits perfectly on the single bed but is too stiff to use with the ribber though it will work with 4 ply yarn but not aran wt - the machine is clean and oiled, the sponge bar is ok - the carriage works perfectly with no yarn - I have tried everything I can think of to do with regard to alignment though the ribber needles seem to be too close to the main bed gate pegs - any suggestions please