Smokepole58Cal
The fly in the lock is either missing or it was installed backwards.
If this is a new gun, call Traditions and tell them what I said and ask them if you should return the lock or the whole gun.
They should be willing to fix it.
When a double set trigger is used, the rear triggers blade moves up rapidly and hits the sear's arm which momentarily knocks the tip of the sear out of the full cock notch releasing the tumbler. The tumbler starts to turn and the hammer that is attached to it starts to descend.
Because the impact of the rear set triggers blade is brief, the sear tries to re-engage the tumbler immediately.
There is supposed to be a very small, movable piece of metal called a "fly" that blocks off the half cock notch to keep the sear from entering it as the tumbler rotates.
If this piece is missing the sears nose will move into the half cock notch exactly like your gun is doing.
Occasionally there is some thick grease on the fly that can keep if from moving into position to do its job.
To see if the fly is there first you have to remove the lock.
To do this, put the lock into the half cock position.
Loosen the screw or screws that hold the lock in place. This (these) are found on the left side of the stock.
Do not remove the screw(s) all the way. Just 3 or 4 turns. Then lightly tap on the screw heads.
This will loosen the lock from its mortice.
Following this remove the screw(s) and the lock.
Once the lock is removed, note the projecting piece of metal that is sticking outward from the interior of the lock. This is the sear arm which releases the tumbler by moving upward.
Cock the hammer to the full cock position watching the pointed end of the sear enter the full cock notch.
Now, restraining the hammer with your thumb, push upwards on the sear arm releasing the tumbler and slowly let the hammer fall.
Watch the nose of the sear.
As it reaches the half cock notch you should see it run into the tiny fly and the fly should push it outward slightly and keep it from entering the half cock notch.
If the fly is missing, broken or installed backwards you will see the nose of the sear enter the half cock notch. If this happens you will need to replace the fly.
Let us know what you find.