This is a common trouble with the T/C and Lyman coil spring locks, their basically the same.
Ok, let's look at the inside of the lock. There is a small piece in there called the "Fly Detent". It fits in a hole in the tumbler under that plate, and looks like a small pointed arrow that moves freely between the full and half-cock notch in the tumbler. With the hammer at full cock you can wiggle it with your finger back and forth a little. It's job is to allow the trigger sear to "skip" past the half-cock notch and let the hammer fully drop.
The problem and the fix;
A couple things can happen here. One, the fly and the area around it can get dirty, rusty or gummed up with old lube and crud. Two, that same area can be just plain dry of lube. Both can affect the fly from moving freely.
Third and MOST COMMON, The 2 screws that hold that plate on come loose. If they are the tinniest bit loose the fly WILL "TIP" and jam the lock just below full fall of the hammer,
(alot of guy's think at this point they have ignition trouble with caps or nipple, because nothing happens when the hammer drops,with repeated cocking and fireing the sear will finaly skip past and let it fall, thus ignition)
,,or as in your case the sear just has to work harder with spring pressure to wiggle past the fly causing that minute pause before the hammer falls.
Take the lock apart, let the hammer down all the way to relax the spring, take a needle nose and grab the spring guide by the tip and push it back to disengage. Now take those two screw out and lift the plate, take care here to NOT lose the Fly Detent, too make it short, just clean everything up in there, lube and reassemble, and be sure to re-tighten those two screws really well.
When I do this, I polish all the flat surfaces with a fine India stone to remove all burrs and make the bearing surfaces smooth for less resistance.
Some times the fly and that plate are worn too much and it's time to use the T/C warrenty,,just contact T/C, send it to them and they'll fix it, free, and send it back,,6-8 weeks. All yer out is the money to mail it and time.
