Eric,
I had a slightly similar problem with my right (rear) 105 STI shifter. It seemed hard to shift to smaller cogs (small lever) and the levers seemed to want to move together. Shortly thereafter a tiny screw fell out. Apparently the difficulty was being caused by the loose screw. You have to push the big lever way in toward the stem and you will be able to see a tiny screw that holds the small lever to the large lever and serves as a pivot point. See if that screw is loose.
Regards,
Raymond
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