The easiest fix is to get the knob al the way in & use a screwdriver on the feed cam screws to adjust the length.You get to them through the top cover on the rightside of the timing belt turn the handwheel around & you see a big headed screw,turn it 1/2 way around & there's a smaller screw that you'll have to use a small screwdriver to get into the hole with.There should be 2 screws in there,one is a short locking screw & you take it out & turn the other one underneath to the right f/a longer stitch,left is shorter,then test sew until you get the length you want then re-install the short one to lock it in.We do have the shaft in stock BUT it's a big iob to change.