Do you know which position shots are low? My 2 cents, I find low shots are usually from two sources,
a.) Imperfect bone support - meaning the weight of your body is not going as straight down as possible, most likely leaning into the gun a bit, causing up and down wobble, so the weight of your body above your hip hinge having to be supported/controlled with muscle tension, and given that is inherently unstable with even slight fatigue, that body wobble transfer to the gun. Keep tinkering with your position -- moving your hips closer to the gun, locking knees out better (kick your heels outward, helps lock your legs better), etc.
b.) A slight impulse into the gun anticipating recoil. I hate the term flinch - it is not a fear response. Your body learns pretty quickly, when my finger does this (pulls trigger) it gets pushed back and compensates for that learned push. It just takes mental discipline and good reps to disconnect that response.