That has nothing to do with denting. Plastic expands when its heated, contracts when it cools, as the cavity cools it needs to draw in more plastic from the runner to prevent dents (why you see it suck down after injecting it). When the gate or runner freezes off (solidifies) before the cavity solidifies it has no way to pull in plastic and sucks in on itself. In other words it is a flaw in the mold design itself, it's always been an issue with that mold, from the day they released it.
Whatever you are doing other than how you fill the injector (it's always baffled me why its been promoted to fill that way, seems like an accident waiting to happen) is helping mitigate the dents.