Is your test fabric the same thickness (ie two layers of cotton plus the same batting)?
Are you wearing gloves so that your hands have a good "grip" on the fabric and you're not adding extra effort to keep your hands from slipping? If your hands are slipping, that creates 'walking' problems.
What stitch length are you using? Try increasing it . Loosen the foot pressure a tad. Also what size needle are you using? If it's too small (or dull) it'll struggle to keep pace.