A new to me P38 doesn't decock.

When I work the slide to cock the hammer and then attempt to decock, the safety moves to the safe position freely and smoothly with the appropriate amount of resistance.  However, the hammer stays cocked.  When I pull the trigger, the hammer will fall, but the trigger stays in the rearward position and is locked.  From here, when I move the safety to the fire position, the trigger unlocks and moves forward.

With the hammer forward or down, and when I place the gun on safe, and when I run the slide hard, the hammer will occasionally follow the slide and come to rest in the forward or down position.  Most of the time however, the hammer remains cocked.

I've removed the slide and inspected the internals.  I am no expert, but everything appears to be fine. With the slide removed, I can press on the safety hammer lowering lever and the hammer will drop.

Does anybody have any suggestions or the name of a good P38 smith?

It is usually the decocker lever itself. This is the part in the frame. This part is different for wartime P-38 and a post war P-1. You can try to bend it up it may help?