Hammer Follows --- but passes safety checks

[adweisbe]

I'll throw this out there. No idea if this is happening in your scenario but it is something I have seen in certain single stacks (Kimber, S&W). The trigger/trigger bow and grip safety are speced such that the trigger bow can actually move far enough to interfere with the sear spring and cause the hammer to follow when the trigger is held to the rear and the slide cycled. This only occurs if there is too much overtravel because the overtravel screw has backed in. On an in spec gun you can throw the overtravel screw out but we don't live in a perfect world.

[Dan Sierpina]

Make sure your Grip Screws didn't loosen up. If they do they can contribute to a hammer following.

This happened to a friends gun. Put a drop of Loctite #242 on the screws when tightening them.

[proff]

It sounds like you have covered the sear/hammer issues. It sounds to me like a trigger bar that is too long. Swap out for one you know works and see what happens.