Mac key mapping broken between 13w42b to 1.7.1

Changing key mappings in the Controls dialog does not produce expected results. Because I'm on a laptop, I normally use L SHIFT for Jump and FUNCTION for Sneak. This works. But when I want to turn off the GUI, take a screenshot,etc., I must press the Function key together with F1, F2, etc. I therefore switch Sneak to L CTRL. In all versions after 1.6 4, this fails – pressing the Ctrl key does nothing. If I change the Sneak mapping to the left Option key (which is reported as L MENU), the Ctrl key produces a Sneak motion, while the left Option key does nothing.