If a level has UMG widgets, swapping to other levels (including the level you're already on) doesn't clear away the UMG widgets.
1: Open any project.
2: Create a new UMG Widget with a Button in the viewport.
3: Scale the button's alpha (under its Color and Background) to 50%.
4: In the Level Blueprint, create a 'Event Begin Play' node chained to a 'Construct Widget' node chained to an 'Add to Viewport' node.
5: Play the level.
6: Open the console and enter 'open Example_Map' or whatever the current level is called.
7: Note that another Button appeared on top of the original. Each time the Example_Map is opened again, the button becomes more visible because they're stacking on top of one another.
Head over to the existing AnswerHub thread and let us know what's up.