Hi & Welcome to the board. Which foot are you using? Viking has a couple of feet that can be used for FMQ. One is a spring loaded hopping foot, another is more like a darning foot. The spring loaded foot can be tricky to install, so double check that. Also, on my machines (I have 3 different model Vikings) there's a specific setting you need to use with that foot.
If you still have the packaging for the foot, double check that it's the correct one for your machine. Viking has a couple different machine lines and sometimes the feet are not compatible
Which needle plate are you using? The single hole or the zigzag? If it's the single hole & you are moving the fabric too quickly you may be deflecting the needle.
Finally, unthread the machine & run it without fabric. If it's still making the noise, I would bring it back to the dealer and let them hear it. It should not be doing this and I would sure be hesitant to continue to use a machine that sounds like metal is hitting metal.