I just bought a Consew 99 zig-zag machine. In a brief test at the seller's, it sewed without a hitch. Of course, now that I have it in the shop, it's refusing to behave itself. There's almost no information online about the Consew 99, so I'm having trouble even figuring out what I need to inspect/verify with it. Here's what I've been able to determine so far.   1) The wider the zig I try to zag, the more stitches it'll skip. It seems to have to problem straight stitching and no problem