Any of the many moving parts in a power clean can be overlooked. Don’t overlook the feet. When reaching triple extension ー airborne ー the feet should slide out to a squat stance, in order to receive the bar in a secure squat position, down in the bucket, with knees out and hips solid. With feet too close, the knees will travel forward in order to compensate for the lack of space for hips to drop into. For you to squat into the bucket, there has to be a bucket.
When moving heavyweight overhead there is a natural reaction to arch the back to get into a better overhead position. This will immediately put you into a BAD position everywhere else. Keep the core tight and ribs down as you send the bar overhead — for a solid base to receive the bar.