This is a somewhat long story, I'd appreciate your patience and advice...

I've been piecing together a 10 speed Campagnolo Record groupset for a project. Buying only NOS parts from Ebay when I had a little extra money over the years. I put everything together and started dialing in the shifting, and found that the shifting performance was very poor. (As a side note, this was probably the sixth bike that I built over the years, so I think I am pretty good at dialing in index shifting). All the drivetrain parts are brand new (new groupset, new chain, new cassette and new, genuine Campagnolo housing cables, and ferrules), and I made sure that the cable routing does not have any sharp bend. Another groupset worked just fine on the same frameset, so I didn't think it was a problem with the deraiileur hanger. The symptoms that I was seeing are described below:

I started searching on the web, and it seemed that one of the common problem with the 10 speed Record shifter is that the carbon g-spring carrier was prone to crack. I took my shifter apart to inspect the carrier , and found that there may have been a small piece that has broken off the carrier. So I order and replaced it with a new aluminum carrier and 2 g-springs. Unfortunately, the symptoms described above persisted.

At this point, I am clueless. A search on the various discussion threads showed that other people have had similar problem with their Campy 10 speed groupset, but I did not find any definite resolution in these threads. Any advice is greatly appreciated!