Hyperflicker issue on desktop

[flbuddymooreiv]

Tested in Firefox Developer Edition 40.0a2 on Debian 8

1. On a moused computer, go here: http://jasonweaver.name/lab/flexiblenavigation/
2. Move mouse to hover over Item 2
3. Move mouse to hover over Item 2 > Sub 1 Item 2
4. Move mouse to hover over Item 2 > Sub 1 Item 2 > Sub 2 Item 1
5. Move mouse to hover over Item 2 > Sub 1 Item 1 without letting the transition from Item 2 > Sub 1 Item 2 > Sub 2 Item 1 disappear
6. Observe hyperactive flicker of Item 2's entire menu.