Probably the trip isn't moving freely due to crud. If you have the right size screwdriver take out the trigger plate screw , flip the action over and catch the spring. If it doesn't come out, use a piece of wire to pull it out. move the top lever to the left. Look to see the orientation of the top of the trip and push it down and out of the action. Clean the trip. You can use a qtip or something similar to clean out the channel the trip moves in. Reinsert the trip, move the lever to the open position and push the trip in far enough to hold the lever open. Put the spring back and then the screw .