Currently, in a Button Template for example, it is possible to get a Default Transition time on the Element's 'CommonStates' VisualState Group.

However, if an adjacent, new Custom Visual State is created on the Element, playing with the Visual State Transitions of both the CommonStates and the Custom Group can cause a XAML error. (attached)

See attached video.

Note that BS-2311 and BS-2311 could be closely related to this.

Repro Steps:

1) Open the 'Z3L_LiveDemo' Studio Project from the InternalProjects repo.

2) On the MainPage, right click on any of the Buttons in the left menu, and from the 'Templates' context menu, select 'Edit'.
This will open the Button Template inside of the Inline Dummy Template Editor.

3) Navigate to the Animation Panel's 'Visual States' tab.

4) Create a new custom VisualStateGroup containing at least one VisualState within it.

5) The new VisualStateGroup will have a Transition time available for it; click-and-drag on the field to adjust its value.
Observe how changing the Custom VisualStateGroup's Transition time, also changes the Transition time of the 'CommonStates' VisualStateGroup.

6) Click-and-drag over the 'CommonStates' Transition time field to change its value.
Observe how a XAML error is generated.
Observe how this Transition time is now out-of-sync with the Custom VisualStateGroup's Transition time.

Expected Results: I'm unsure, but it seems unexpected that the Transition time of a Custom VisualStateGroup and the CommonStatesGroup are initially linked as observed in Step 5)
Expected Results: Changing a Transition time should not generate a XAML error.