sometimes lifting the foot up and turning the needle control forward and backward (not actually piercing the work), whilst you "gently" pull your work out is enough so that you can cut any unwanted cotton holding the work on the machine. This type of jam usually happens when the machine is working in the same spot, not advancing. You may want to check on the serrated "lifters"..the parts on the machine arm which lift up and move your work forward or backwards. They sometimes get filled with all sorts of fluff and scraps.. to get to them you may have to unscrew the top plate on the machine arm (where the needle inserts)give them a good cleanout with a brush, then oil them with machine oil.