In GarageBand 10.0.1 (2013), I frequently will get "stuck notes" (i.e., a certain key will continue playing as if held down when it is not) when playing my Akai MPK 25 connected via USB. I have noticed that GarageBand receives the "note off" signal, because when recording and a stuck note happens, the sound is not recorded onto the score or registered on the track. Furthermore, the "stuck note" stops if I press the "play" transport control, even if there is nothing in the song.

Thus, it appears to be a Core Audio issue of some kind. I've tried some tests with the "Midi Studio" window of the "Audio MIDI Setup" application. If GarageBand is open in the background, notes will stick if I persist testing long enough, but the note off chime always plays at the right time when keys are physically released.