Do you have thin .. very thin... batting in your quilt? Some machines just don't have good space between the foot and the bed of the quilt. I've taught freemotion for over 10 yrs and have seen a lot of machines. I can sit at some where people are having trouble and know that the machine is just not made with enough space.
you might take it into a store or service place with your quilt sandwich and have them try it since they know what it is supposed to feel like. The fabric should FREELY move.. you should not have to pull or tug it at all..when it's not running you should be able to easily move your quilt. I have a few youtube videos showing me quilting.. you can see how easy it should move