Is the walking foot made especially for your machine? Last year I bought a generic walking foot & it left a little dusty grease trail on my white fabric. The only way I got the marks off the fabric was to use dish washing liquid that had bleach in it. Of course, my fabric was white, and I wasn't too afraid to use that. I returned that walking foot to the fabric store. I went to another store and bought a Brother walking foot that would fit my machine. It was explained to me by the Brother dealer that walking feet are made to match the machine's dog feed to work together to feed the fabric through, and a generic foot may not work because it doesn't match up and your fabric may bunch. Anyway it cost me more money to buy that walking foot, but it solved my problem.