You Bend Your Arms Too Early

The arms start pulling before the legs and hips have finished.

Why it happens

Early arm bend kills the transfer of force from the floor. The arms are cables during the pull and become the thing that moves you under the bar only after the extension is done.

The fix

Drill the exact range of motion where the bend happens. Practicing the part that breaks, rather than the whole lift, is what makes the habit go away.