Here's another thought - just by looking at the gun, the one thing that jumps out at me is that the gun has been modified. The red ramp in the front sight was never standard on the early model 60s, and this was a popular aftermarket mod in the 70s and 80s for guns that didn't come so equipped.
my point is, it appears to have been at some time in the hands of gunsmith, and it may be coming down to changes he made elsewhere to "slick up" the gun.
Also, are you measuring the b/c gap at lock up per the instructions? Have you also measured the endshake? A .003" b/c gap with no endshake at all would possibly lock up like that.
Another idea is to see if an endshake bearing washer has been installed to tighten the b/c gap. If the yoke screw is not positioning itself correctly, it may be because of the assembly's relative position being altered by an endshake bearing by a gunsmith. Removing it could easily open the b/c gap back up or restore some endshake so the gun operates properly.
A final thought, the new screw you get may not match - If Brownell's sold you a Yoke screw "assembly," it is likely off of a later model gun as this part went through revision in the late 80s in that area. I would try to get the existing screws sorted properly per Jim Keenan's instructions. If I recall our prior conversation about this, you gun was built in 1978 I think (I can see that it will date to 74 to 81 or so from the picture).
I hope this is of some value.