Sewing Machine Not Sewing a Zig Zag Stitch?

I have a Husqvarna Viking #1300 that I was fortunate enough to receive from my sister-in-law. It had been working flawlessly until I was making my daughter's costume. I'm new to sewing (three months) so I'm not sure if it's something I'm doing. I have, however, checked my upper threading, bobbin threading, presser foot tension and thread tension, I also cleaned out the lint from under the feed dogs.

Here's the problem: It will only sew when the needle is on the right. When sewing a zig zag it will pierce the fabric the entire z, but will only make a stitch on the right hand side.

By Marcellina