Agree with Operator. I had this happen with a ST-5600 "double/triple" compatible shifter. It's a pretty common problem. Not sure I'd call this a design flaw, more likely bad judgement to use a triple shifter on a double setup by the bike manufacturer. It probably seemed appealing to not have to spec a specific 2x or 3x shifter depending on the bike setup, but this has clearly caused a lot of problems. I just had mine waranteed out through my LBS a few months ago, but Shimano will accept the returns directly through their returns line as well. LBS may be able to save you the shipping cost though.