Problems w/ admin bar + customizer

When I activate this plugin, two problems appear:
* The admin bar on the main site front pages disappear
* The tool at Appearance > Customizer no longer shows a preview

The problem disappears when I de-activate the plugin, clear my browser caches and re-login, and re-appears when I re-activate the plugin, clear my browser caches and re-login.

Our install is pretty vanilla WP 4.3 multisite (domain). The problem shows even after de-activating all network and site plugins, widgets, and switching themes to un-configured/unaltered twentyfifteen.

* Can you folks please investigate?
* How can I download the version?