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If the knees are moving out as the hips move back and the femurs externally rotate, their forward travel will be limited to that which is normal for your anthropometry in a correct squat, where all of the forward knee travel occurs in the first third or half of the dissent. After that, the knees just stay in place and the hips account for the rest of the movement. So, from the very top, bend over, shove the knees forward *and* out to the place where they will end up, just in front of the toes, and stop them there; the rest of the descent will consist of the hips moving back and down.
It would be better if you filmed your squat from 45 degrees behind you. We can't see your full setup or all that is happening from straight sideways.