a couple days ago i took my handle bars off to see how they compare with a ligther set. when i put them back on and reassembled my bike i noticed that when ever i press the button on my sram x.7 shifter to downshift that the button doesn't pop back up any more for some reason. i have to manually push it back up.

what could have caused this? the cables look fine. is it the derailleur? the shifter?