Mouse input breaks for CommonAnimatedSwitchers when inside retain-rendered RetainerBoxes

Development Programming & Scripting UI
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Steps to Reproduce
Create a UMG user widget with the following structure and (non-default) settings:

  • Root
    • RetainerBox : RetainRender = true
      • CommonAnimatedSwitcher
        • [subwidget] CommonActivatableWidget
          • Button
        • [subwidget] CommonActivatableWidget
          • Button

Add logic to forward the On Clicked events from the buttons in the subwidgets to the parent widget, and use them to switch the active index on the switcher.

Notice that when you run the above, the first click will switch from index 1 > 2 correctly, but then the button on the widget at index 2 will be inactive, not responding to clicks or hovers.

The issue seems to be an interaction between the retained render path on the retainer box and the animation on the CommonAnimatedSwitcher; if you turn off the “Retain Render” flag on the retainer or set the “Transition Duration” to 0 on the switcher, it’ll work fine.

In my example project, the top half of the widget is _not_ retained and cycles between magenta and cyan pages as expected. The bottom half _is_ retained and you can swap from red to blue, but the button on the blue page is non-responsive.