Teensyduino 1.15 does not support "Keyboard.releaseAll()" for the Teensy 3, even though it is supported for the Teensy 2 and Leonardo:
http://arduino.cc/en/Reference/KeyboardPress
The obvious work around is to use Keyboard.release(), but it is convenient to have a single command that releases all currently pressed keys.
http://arduino.cc/en/Reference/KeyboardPress
The obvious work around is to use Keyboard.release(), but it is convenient to have a single command that releases all currently pressed keys.