I would start with the following:
1) Try and bear down on your abs tighter in the setup.
2) Get your wrists straighter with middle knuckle pointing up.
3) Don't hold the lockout so long. Just a solid second is needed, then back down. You are holding it longer which is causing you to sway/loose tightness/use your traps longer than needed.
4) Be careful not to push your head/neck forward too much during lockout. Keep them more neutral.