Modifiers are discarded when pressing hotkey. This will happen on MacOSX after you click on any text field to take focus.

Repro:
1- Open attached project.
2- Open scene 'asdf'.
3- Click to get focus on the hierarchy window and press "Shift-Space". Layout should expand. Press "Shift-Space" again to go back to default layout.
4- Now, select any game object.
5- In inspector, click on text field position.x (from this point on, you're in corrupt state).
6- Try to press "Shift-Space" again to expand hierarchy window and see that it won't work anymore.

Reproducible: 2017.1p2
Not reproducible: 2017.1f3