Problems Using Concealed Zipper Foot?

I bought a generic concealed zipper foot to use on my Janome DC3050 machine. The left side of the zipper was stitched perfectly, but I had great difficulty with the right side, including stitching though the zipper teeth. I borrowed another foot from a friend, but had the same problem. In looking carefully at the foot the needle seems to be slightly over to the right resulting in it stitching through the zipper teeth. I changed the needle in case it was bent, but still no luck. Could it be that only the Janome zipper foot will fit properly or is the needle out of alignment? Help, please.