Repro Steps:

1) Open the Z3L Sample Project
2) Select any of the Main Menu buttons on the MainPage, right-click, and enter it to edit its Template.
3) Navigate to the Animation Panel, and select the [AnythingToMouseOver] Visual State transition. This will cause the Animation Timeline to appear.
4) Select any Keyframe on the Timeline. This will cause the Keyframe Properties to appear.
5) In the Keyframe Properties, click the EasingFunction for the Keyframe.

Observe how the EasingFunction dropdown doesn't remain open, and instead, switches between EasingFunction types.

6) In the Keyframe Properties, instead of clicking, perform a click-and-hold on the Easing Function dropdown.

Observe how the EasingFunction dropdown remains open until the left-click is released.

Expected Results: Clicking (without holding) on the EasingFuntion dropdown displays the entire listing of EasingFunctions and doesn't close until a new Function is selected.