I just had an 85 C installed in a 20-yr-old 75 D Compact. Now I only have double-action at half-cock. The trigger only resets when the slide recoils or I cock the hammer. It will reset when I just barely pull the hammer back, just the smallest amount of pressure.
The adjustment screws are in. Nothing else was changed. I tried changing the screws, i.e loosen/tighten. No change.
With the slide off I can see the rear of the trigger bar pop into place or reset when I give the hammer that very slight pull. It seems like something isn't right back there.
The rear of the trigger bar is just over a millimeter below the bottom of the ejector until I put a little pressure on the hammer. Then it pops up to contact the bottom of the ejector. Or, at least that's how it appears from my perspective.
On my P-01s I see that the rear of the trigger bar is up against the bottom of the ejector.
When I pull the trigger when in the un-reset position, it lifts what I think is the firing pin block lever. But isn't engaging something beneath that until I manually reset with the hammer. I can see in my P-01s that the firing pin block lever isn't lifting until the hammer is fully cocked.