Originally Posted by LarDasse74

Have you tried swapping your derailleur for a Campagnolo on their 'approved list?'

I have not tried the combination you have, but I have experienced a similar feeling with Shimano shifters. The shifters turned out to be alright but I was mal-adjusting the derailleur and just making it impossible for the ratchet mechanism to work. I can understand how a difference in cable pull can cause a similar problem.