Left/FD 7800 brifter has stopped returning when shifting from small cog to large cog. Still shifts fine, just have to pull it back into place. What spring/cog is responsible for loading the return mechanism on lever "A" (the front metal one responsible for small to large cog shifting)?
Have previously disassembled and replaced an interior spring when it snapped, which prevented the tooth from engaging and locking the cable in position. I say this only to relate that I can open it up the shifter, disassemble and re-assemble just fine. I have the exploded view from Shimano; however, it fails to show the internals. Obviously these shifters are not meant to be serviced. Naturally, that just makes servicing them that much more fun. Ok really its infuriating, but its worth the time/money saved.
That will teach you to go Campy. The 2009-2010 ultrashift levers are simple to take apart and repair. You can buy all the guts in the back half for $37. Take all of 15 minutes to replace (after the shifter is off the bike).