I need helP! Everytime I sew an invisble zipper on one of my garments, they get stuck and won’t sip up. They never zipe up when the dress is on the dress form. I have atleast gone through several zipper and ruined a number of dresses. What can I do? I am not usuing a special zipper foot but I might but. I have a Husqvarna 310 and it has 3 foots but noe descriptions of what they do but I think one is for invsible zippers and I have been using it all this time. Any help, please!