Look in the direction you're going on heel side. You're looking down hill. You wash out every time.
I'm assuming your knees are staying nice and flexible.
I had the same problem.
I usually do keep my eyes ahead of me (in the direction of travel) but when the board starts chattering I think I do instinctively look in the downhill direction. I will definitely try to be more conscientious of this but I'm still pretty sure I'm doing something else wrong too.