Here are some pictures, I got the bike a few months ago and the reason I put the Teflon tubing was to prevent damage to the paint but I was getting miss shifting up and down using a veloce brifter, finally after 2 days dealing with the problem i got it almost right, then a friend needed brifters so i sold them, afterwards I got a brand new centaur ones. After reading here I added oil in a few places like the Y part inside of the shifter but i was not suspecting that the Teflon that is designed to help friction was my problem shifting down. That's why yesterday I added some oil inside the tubing and the problem was gone immediately. Just in case the Teflon i have there is for brake cable, not for shifters, slightly longer diameter, the cable pressure keeps the lining in place.

Doubt u guys can notice but anyhow... the 1st one is the Y piece we are talking about, I put some oil in there while passing the cables and after wards while testing the shifting also.






ps: another thing that mess the shifting is that when closing the quick releases, the derailleur gets out of alignment, the hanger moves. I have seen that several times also.