Dumbbells drift forward from the legs
Without the bar to guide the path, dumbbells swing forward increasing the moment arm.
Overactive muscles
Erector spinaeLatissimus dorsi
Corrective work
Foam RollLats↗StretchHamstring stretch with strap↗Without the bar to guide the path, dumbbells swing forward increasing the moment arm.
Hamstring flexibility limits the hinge; lumbar flexes to increase depth.