Originally Posted by WhyFi

I think that he's talking about 5600, which evidently had a pretty problematic front shifter when paired with a double. The internals on mine broke early on. When I brought it to the shop, it wasn't at all unexpected - they, and Shimano, had seen it happen plenty of times and it was replaced with a double-specific iteration (5601 IIRC) that they'd released presumably because of the problems in the wild.