The lever has a little hook that engages the triggerguard opening. Sometimes the surfaces of the hook require a bit of fitting; but usually not though.
I would not think of the spring in the lever area, unless it is unusually weak in unlatching.
Other times, the forward motion of the lever hook is impaired by the front section of the finger lever, ie in front of the screw there. It should allow the hook to engage fully on its surface to the edge of the trigger guard. If one moves the lever and watches the hook in the triggerguard, you can see the hook engage the triggerguard opening's surface, this is controlled by surfaces forward of the screw and trigger guard engagement surface on the little lever, the one you move.
