Is there a DA sear even in the gun?
Maybe it was left out after the work on the hammer to case color it and the trigger.
No DA sear,,or sear not in position because the spring is missing or damaged..... The trigger continues it's motion,,cylinder revolves,,but hammer sets right back down again from that just slightly cocked position when the trigger returns forward..
I'm assuming from the desciption of the gun before the work was done had a plated trigger and hammer..and that the hammer (and trigger) were stripped of plating, polished then re-colored.
Any polishing of the hammer may play a role in this especially if the DA sear was left attached to the hammer during the process.
Polishing by use of a buffer can be quick but it can also damage lots of things including sharp defined edges. The front edge of the DA sear is angled just right for the trigger to pick it up and rotate the hammer.
If that Sear has been reshaped by polishing over the surfaces for any reason, that may have changed the angles and/or length of the tip.
There isn't a lot of difference betw an angle where the trigger picks up the sear and rotates the hammer with it,,,and an altered angle at the tip where the trigger mearly skips off of the tip and leaves the sear w/hammer behind.
The small DA sear is pinned to the front face of the trigger and has a tiny coil spring behind it.
Perhaps the sear and/or spring were not replaced back in the hammer after the CaseColor work was done.
...or maybe the DA sear with spring was left in the hammer when the plating was stripped and then the Case Coloring done.
If this is so and the case color is the real stuff,,the 1400+F needed to run the process would have annealed that tiny spring to worthlessness.
Some re-case color work to small parts is often done with coloring chemicals and not putting the parts thru the high heat oven char treatment.
Even so, stripping plating, then polishing and recoloring with a simple chemical process can churn up a lot of gunk that can get in behind that sear and cause problems if it wasn't removed during the work
The remains of an annealed spring if left in place would simply crumple upon the first couple of DA cycles. It's dead soft fine wire at that point.
That could leave the sear itself jammed in the 'in' position. The trigger would miss it upon DA cycling and leave the hammer only cocked a few degrees of rotation.
Dis-assemble the gun and see if the DA sear is even there on the front face of the hammer.
If it is, see if it pivots under spring pressure while in place and springs back out again freely.
Watch and see if the trigger engages the DA sear.
Just some guesses on my part of what could be happening just from the description of the condition of the orig gun finish and then the work done to it.
You should be able to see what is not working correctly when the action is slowly cycled w/the side plate off.
If you want to, remove the mainspring for cycling the action with the side plate off,,use finger pressure on the hammer spur to replace it.
Much easier to deal with when trying to hunt down a cycling issue. Plus the hammer and trigger pins aren't left unsupported under mainspring tension.
