After clicking in top-left corner of screen, sidebar won't open

Although I run into this in various other situations, the following is the most consistent way I can reproduce it:

Set to Unity launcher to auto-hide (Appearance | Behavior tab | Auto-hide the Launcher -> On, Reveal location: left side, reveal sensitivity: default)

* With no open windows (i.e., desktop visible), click in the very top left of the screen

* Attempt to open launcher by pushing into left edge of screen

Expected: slight shadow appears when cursor touches left edge, and launch appears after pressing into the edge

Actual: nothing happens, no amount of pressing into the edge will open launcher

* Double-click on the desktop: Launcher will now open fine

This is especially disruptive given that the top-left corner is where the close-window button lives: the workflow of "Close window, go to launch to open different task" consistently triggers this.