Throttle should be closed with a spring on the control line, not from strictly the servo itself. Looking down on the servo, the throttle is on one side of the arm and the brake is on the other...180 deg apart. I don't have mine together right now but here's a pic of the linkage...your's may be flopped around but with the spring setup on the motor linkage the throttle closes with the same force all the time. Most are setup like this but in case yours isn't I posted a pic.

Another thing to consider is the hex nut around the LS needle may have come loose not allowing the barrel to close.