Plus say your knot is not uniformly tightened ,or is cocked off to the side changeing the pull from center to side.
Hrm, this leads me to ask 'what knot?'

I never tied a knot in the channel with my whoopie slings. I just ran one end through, then did a hitch by running the other end (the adjustable end) of the whoopie slings through the eye loop and cinched it down.