I have 2005 Chorus 10 and this doesn't happen to me. It will go the number of clicks and stay in that gear. If I overshift it will just fall into place. Maybe you have a weak part internal to the shifter that doesn't catch. Or is it jumping to the next cog without a click? In that case it is just settling in, but that would sound like a cable adjustment is in order. Each click should leave the chain centered on the cog.

I rented an Ultegra equipped bike this past December on Maui to do a ride up Mt. Haleakala, and it drove me crazy that I couldn't multi shift. Plus the lever on Ultegra is reversed from Campy so I was always going the wrong way. I got used to it after a few days but was glad to be back on my Chorus setup when I got home.