Hey. Just bought a used tandem with Ultegra components and am having an issue with shifting the front deraileur. When riding, if I try to change to the large chain ring from the small it requires me to fully push the brifter twice before it fully moves. The first push it goes halfway (and makes noise like crazy) and the second push moves it over. Downshifting and trimming all work fine. I have tried adjusting the H/L screws but it has no impact. So, what do adjust? Tension? Where?