Chatter is caused by a lack of pressure management. Most likely this has to do with a rider's alignments not with the board being ridden. being broken at the waist, not actively moving through the turn, being misaligned to the front foot, leaning to much, etc.... can be causes.
I would start making sure you are progressing through your turn first, and not becomeing fixated down the hill. Next I would try and feel If I was prgressively tilting my board and flexing or extending through the turn. Think like ratching the binding. Is my board picking up from the snow a click at a time? All at once? Does it stop when I could still tilt it up while I am still trying to turn?
For further assitance try let us know when in your turn the chatter happens. Is it early in the beginning? in the middle at the end? Does it happen between the feet, closer to the tail or maybe closer to the nose? Any other details would be useful.