Lower Back Pump with Kettlebell Swings. Help?

Hey i wanna start doing kb swings, but every time i do, i get a nasty pump im my lower back, near left quadrorum. i asked few coaches to look at my technique and thay all say its good. so im asking if someone has experience with this, like good warm ups for swings, stretches, tips etc.
also pls dont move this to conditioning or injury threads cause theres almost 0 activity there

glute activation drills in your warm up

Check out steve maxwell’ s Kettlebell courses, he has been doing it long before crossfit, 30 plus years.