Campagnolo 10s Shifters Soft/Slipping Shifts Even After Rebuild

[brewsmith]

I currently have two sets of Campy 10s shifters that I am trying to breathe life back in to and having some issues.

Two of the left/rear shifters have very soft shifting and will even slip a few gears when I put tension on the cable manually. One of the front shifters also has the same issue, with very 'faint' shifting. I just rebuilt one of the rears with fresh springs after finding that the post on the spring carrier had snapped, but upon reassembly, the issue was only slightly improved, and still not up to snuff.

My questions therefore are:

What part of the shifting mechanism is responsible for this ailment? Are the ratchet mechanisms worn down, do in need more/better/different lube/grease in there, is there something I can do to better engage the thumb lever?

Secondly, to date, I have been using functional, but cosmetically challenged levers as a source for parts. This may be a contributing factor, since the rebuild parts are not new, but they did appear to be in good shape. Is a source anywhere for the rebuild kits (EC-CE110)? So far I have been able to find pairs of nice levers for ~$100 and any rebuild kits available are almost the same price (if you can find them), which negates the benefits of Campy's ability to be self maintained...

Thanks in advance for any sage advice