Needle arm loose

Question

I have a Bernina Deco 600. When I try to embroider, I hear a knocking sound and the machine stops. I looked inside and it lookks like the needle arm is hittihg the frame. When I grab the needle arm it will move up and down and twist a 1/4 turn in either direction. How do I fix this. I need to fix it soon because of a time sensitive project. Please help. [e-mail]