Some machines need to set the stitch length to 0 for FMQ and the quilter controls the stitch length. Some machines, like my Baby Lock, need to have the stitch length set to their regular length (or even a little larger) for FMQ.
If it is situation 1 with yours, then it sounds like you need to find the sweet spot between motor speed and how fast the sandwich gets moved.
If it's @2, then you can easily try by bumping the stitch length.
Good luck - it takes time and many many trials.