The safety bar (like a transfer bar), Part #5 in the Numrich schematic -they call it the 'Safety) may be deformed a bit or otherwise jamming in it's slot in the frame.
It's pushed up and down by the 'Lever',,part#7.
This all sits on the right side of the hammer in milled slots & channels in the frame and works off of the motion of the Trigger.
Simple short, small dia pins running in the slots in that Lever make things work. The Lever rotates on the hammer pin, the large hole in the part.
Just a guess, but pulling on the trigger and letting the hammer fall on it's own may pull the 'Safety' down harder and further and to a point where the Safety is jamming in it's lower position.
Dirt, deformed Safety edges. or both,,the Safety sticks there. That holds the trigger in the rear position unless the lower arm of the mainspring is strong enough to push it back and return it forward.
It could also be in that "lever' or it's cut-out in the frame or those small pins that connect the parts. They do wear out.
Gently pulling the trigger and letting the hammer down puts no or very little stress on those parts and a bit less movement.
Perhaps they don't get pulled or pushed to the point where they jam in position.
(The lower arm of the mainspring does not work directly against the trigger, but instead it powers the rebound lever. The rebound lever inturn powers the hand. The hand being pinned to the trigger, the trigger also benefits from the spring tension and uses it as a return spring.
Lots going on inside the old style Colt DA.
A good cleaning can really help and is always a first step in their repair.
Those parts (Safety, Lever..) are among the last to be removed from the frame in a complete dis-assembly being 'behind' the hammer.
Take care removing the V mainspring. They come out easily if done correctly as well as re-installing them.
Horsing them out, they can break very easily as well.
No pliers
