ecu box problem

Junk yard connector ? The round female terminals inside the harness connector might be stretched in diameter and/or corroded. New are available. And like their other round female terminals, they were ovaled. So on a round post, contact was at 2 straight narrow lines instead of all the way around.
The screw in its center ... about worthless. Over tightening will draw the nut right off the plastic post its crimped to in ecu. Maybe the connectors never did fit really well. Thus a screw to keep it from falling off where the box is mounted vertically.