Lower back pain with deadlift but not squat

I am 27, 6'1" at 205 bodyweight, been training for about 3 years. Current lifts are 500/315/555 (S/B/D). I have been experiencing lower back pain on my left side (dominant side) when deadlifting with weights around 405 and above. I am confused mainly because I thankfully have no day to day pain and no pain during heavy squats. The pain is not shooting and responds well to stretching and massage. The technique flaw that I am aware of is that I have a slight tendency to tuck my pelvis at lockout. Could this be causing the pain? I.e. not loading the hamstrings correctly?

Any insights or suggestions would be appreciated. Thanks.

Video?

https://www.youtube.com/watch?v=WK6eSwCcZpM

No pain on this, but definitely does not feel normal.

You are not setting you low back before the pull. Step 4.

I was discussing the tendency to try and use momentum to get the pull started. It’s counter intuitive to squeeze it off the floor slowly and it’s really difficult to overcome that natural tendency to bully it off the floor just to get the reps over.

I do a lot of volume DL work at around 80% of 1RM (5x5) followed by RDLs-all using straps. Initially my lower back was badly fatigued during the lifts and sore for several days after. Once I stopped bullying the bar off the floor and started properly setting the lower back each time, the fatigue vanished, as did the soreness.

Worked like a charm. Thanks.