Emu XL-7 & MP-7 User's Group

Hi everyone.For a while I've had this problem with data wheel on my 
xl7 where it would throw data all over the place unless turned really 
slowly.I've tried deoxidizer but that would work anly for a day and 
it just comes back to same problem.I would really like to fix this 
somehow.Does anyone else have this problem and can it be fixed easily?

Thanks
Nermin