The global and local dropdown TOCs do not work properly. You can check this even on your Sphinx Sample page.

The reason seems to be -- as far as I found out -- that in _static/js/jquery-fix.js the variable jQuery is unset after .noConflict(true) returns.

I am not really familiar with jQuery but it might be a problem with its upgrade. On Bootstrap Theme Demo under the older jQuery version it still works fine.