TextBox widget renders differently when in a Retainer Box

REGRESSION: Yes, does not occur in 4.15.

When a TextBox is wrapped in a Retainer Box, it appears faded when rendered in the viewport.

1. Open QAGame in editor.
2. Open the level TM-UMG.
3. Open the Widget Blueprint UMG_Optimization.
4. In the Hierarchy, right-click the Optimized vertical box and select Wrap With > Retainer Box.
5. Compile and close the Widget Blueprint.
6. Open the Level Blueprint.
7. In the Create Widget node, set Class to UMG_Optimization.
8. Compile.
9. Play in viewport.

RESULT

The TextBox under Optimized looks faded.

EXPECTED

Both the Optimized and Non-Optimized TextBoxes to look the same.