10 speed campy ergo lever

Question
when shifting the right hand ergo lever thumb control down to change gears from the top cog,23 to the next cog 21, the chain is dropping into the bottom cog,12th cog, without ant incremental shifting. The lever shifts up the block without a problem it is only when i shift down that there is one click and that is it. I have checked to see if something is restricting the lever and i have also sprayed into the lever to dislodge any dirt they maybe inhibiting the lever.No change. The gear cable is going slack, resulting in the chain moving to the smallest cog. I have replaced the gear cable incase there was some buring but this also has made no difference.could it be a spring that has broken and needs to be replaced?  

Answer
Hello Jennifer,

Thanks for asking me this question, but this is one you can't explain in little words.
When shifting down and the gears are jumping from 23 > 12 it must be a spring or a adjustment in cables/derailleursettings.
Also a matter which is important, how much miles/kilometers are ridden with these Campy gear?
Maybe it is easier to ride to your local bike store (lbs#, and let them fix it in a short time. I think and believe that it is a little thing what bugs you #but very annoying).

Hope to hear from you the result.

Best regards,

Mick