macbook keyboard issues with y, u, i, o keys -- On the most part there are two issues that cause a keyboard key/s failure a liquid spill (or food crumbs) or the battery is pressing up from below. If you only have one key failing I would pop the keycap off and see if dusting out any crumbs or with a cotton swab (Q-Tip) just barely damp with isopro... - MacBook Pro 15" Retina Display Mid 2012 #mac #issues #pub