What he said!!!
We can discuss training possibilities for decades and not even reach the precision of one simple video analysis. Please have a sagittal(side) + frontal video of your technique at full weight for us to see what may be wrong.
Possible worst technical flaws would be suboptimal hips extension and bar too far from the body, they are related. When you past the knee, EXPLODE!!! (second pull)
BTW- Jumping rope is a nice “feet” exercice that would be rated as a very low intensity SSC. The goal would be energy efficiency and move with as much less muscle energy as possible. In PC, hips extension is way more important than feet so you must already know my answer…