Right campagolo gears slipping I have a set of Campagolo Athena 11 levels and the right one is slipping when changing down.  What is the problem and which part do I need to replace, please
There's a few different reasons for this. Without knowing the exact method of cable routing for your brifters (yeah, I went there) then the instructions could me re-wrapping the bars or fishing cables out of your frame, but i'll order them in least amount of work first (and re-suggest above already failed instructions for reference)

Make sure it is actually the brifters not malfunctioning and not the derailleur getting caught on something or chain having a stiff link.

1. Cleaning the shifter while on the bike

The best method of going this is properly giving the insides a de-grease and re-grease.


Get some water soluble de-greaser in a spray can. Gain access to the mechanism by going from underneath or pressing the brakes.
Spray all up inside the shifters, break down the grease and crap stuck to it.
Flush out the inside with water. A jet-wash is probably too powerful for this, it can bend metal, but a hose with a directional powerful spray will probably work.
Dry the insides. Use an air compressor, or what WD-40 was intended for (water displacement!) and wait for it to properly dry
Spray in a medium heavy grease, white lithium grease is available in a can. Spray a little in and move/shift a few times, then a little more. Don't overpack it, but you want a reasonable amount.


If this doesn't work:

2. Replacing gear cable inners

Sometimes water and other debris can get into the inside of the cable, or the wires can fray, causing drag or slip from not properly engaging.


Shift into 11th gear (assuming regular derailure pull) so the cable is slack
Remove the access caps for the cable, losen the pinch bolt on the derailleur and pull the cable all the way out through the brifter
Replace with a good quality inner cable. Standard is 4mm.


If that doesn't work:

3. Replacing gear cable outers

The inner coating of the outer cables can wear away and make shifting slugish or stick. Once this happens they can catastrophically fail and no shifting is possible.
 - After removing the inner cable (above)
 - Replace the outer cables (you can reuse the ferrules if they're not damaged) by cutting them to the same length with as old a dremel or proper cable cutter so you don't crush the ends.
 - Re-insert inners as above

If that doesn't work:

4. Removing brifters for proper cleaning/disassembly

Looks like you've ruled out everything else and you need to get aggressive on these before you bin them.


Get them off your bars
Soak the whole thing in white/mineral spirits for a while. Give them an agitate them and see how much dirt/grease comes out.
Brifters are super-hard to disassemble and there aren't normally guides from the manufacturer; they expect you to buy new ones. If you do attempt it: take loads of pictures, keep parts/springs grouped together and be prepared to have to re-make any small parts that have failed, it's doubtful you'll be able to get them from the manufacturer.


Final thoughts

I've got pretty in-depth here, but I think I've written down some of my experiences for cleaning. I've never taken apart a brifter before more than replacing a front-cap so I can't say if that's likely to fix it.

If you go ahead with any of it, let us know which methods were more effective for you.