Is this new or has it always been going on? Some machines do pull more than others.
You've already done the basics of cleaning? Sometimes lint can build up.
My 301 is a pretty steady little workhorse with a good 1/4" seam, but on my other machine I put a small fancy kids bandage on the throat plate for my 1/4", the little bump of the bandage helped in addition to the visual of the tape to help keep me on track.