I have the same issue on a Jamis Xenith Comp with Shimano 105 compoents, except for the rear derailleur which is Ultegra. I bought it used a couple of months ago. Someone did the adjustment for me on the rear and it no longer shifts on its own like it used to, but I still have initial trouble shifting to the larger chainring. If I'm going downhill and am in a large gear I can do it, but at first attempt on level ground it won't go, and this chatter happens instead, until I press the smaller level as if to "cancel" the attempt. I bought a bike maintenance manual and will take a look at this link too, but any advice is hugely welcome.