Ultegra 9-speed brifter upshift problem - beyond WD-40? I have a 2000 Ultegra 9-speed right/rear brifter that does not "release" the cable properly. 

My initial search on this problem suggested that this could often be cured by flushing with WD-40. So I've done that, and the problem persists. But after comparing the operation of the right brifter with the left I got more insight on the problem.

It turns out that if I hold the outer lever vertical (i.e don't let it move), then the inner lever clicks and releases properly. But if I don't hold the outer lever, the inner one will eventually start pushing the outer lever around without the inner ever clicking.

So it seems to me that there is an arrangement like this:

Outer lever -> Inner actuator -> Inner lever

And there is supposed to be something between the outer lever and inner actuator that is offering resistance to the movement of the inner actuator so that the inner lever will be able to, umm... actuate the actuator.

So, is there an obvious adjustment or missing part that I should be looking for here. Or just more WD-40? It seems like the problem is not enough resistance, not too much, so it doesn't seem like a lube problem anymore.
This link may be useful to you if you really want to dig around inside your shifter; though it looks like it might require a few special Shimano tools. Also note that he only has full strip/rebuild info for Dura-Ace...though I would expect Ultegra to be substantially the same, differing mainly in the use of plastic instead of metal for some parts.

Also consider that it is pretty easy to find Ultegra 9 stuff on eBay and elsewhere, and it may be more time-efficient to just replace rather than repair.