My first answer to improve a lift would be to do it more often, however it's sure that if you taking the time to improve your weak links it will help you quite a lot.
If it's the quad that taking you back, i'd suggest you do some pause front squat or anderson squat that will simply take out the strech reflex.
If it's the back/core because you cannot maitain au proper position, there are breathing squat that help to like it's say breath properly and zecher squat that i like the most.
And you can add some speed work with fast reversing between the eccentric and concentric phase that would desensitive the golji tendon and help you utilizing the stretch reflex.
Hope it'd help you and understanding my english was not so hard.
Have a nice day.