I just updated to 2015.4 (184.108.40.206 Build) and it appears that the Option-click style in panel to clear overrides no longer works. I rely heavily on this quick key! Is there another way to quickly clear overrides?
It still works here, and should for you too. First thing to try is resetting you preferences:
Trash, Replace, Reset, or Restore the application Preferences
Also consider it may be interference by 3rd-party keyboard, clipboard, browser plugins or utilities...
No problems here in InDesign CC 2015.4 on Mac OS X 10.11.5.
Try restoring your InDesign preferences. Here's how:
Retrieving data ...