I had the same problem and bought a new sponge strip. That fixed it. It cost £5.00 and took 10 minutes to install. The only problem was when I took out the old strip then turned the machine upside down, all the needles fell out over the floor! The Knitmaster spares aren't made any more but a Brother sponge strip fits perfectly with just a small piece needing to be trimmed off the ends. I love my Zippy and use it for all sorts of hand knitting yarns.
Marion Bucks, England