The 'D' key, to the right of middle C, seemed to be stuck down.. I watched her fingers, and she definitely wasn't holding it down.. and yet there it was.. still depressed. As she finished playing, it popped right back up, and I began to wonder how long it had being doing that..
I had a quick play afterwards, and concluded the key was just 'sluggish'.. sometimes it would come right back, other times it would stay down.. there wasn't any reason to it, just random chance. Of course, from that point on, if I tried to play something with 'D' in it, the key would behave fine unless anyone else entered the room. Perhaps I had a psychic key malfunction.. or perhaps this was about to get expensive..