Reproduce: 1. Open some windows 2. Click Show Desktop widget 3. Click to open Plasma Menu 4. Choose Leave => the logout bar (the one the with timeout) appears but is barely readable because the windows previously hidden are now have-transparent overlapping.
Might be related to https://bugs.kde.org/show_bug.cgi?id=352988
Has nothing to do with Folder, reassigning.
Created attachment 96307 [details] Correct behavior
Works fine for me. The windows just stay away. plasmashell version 5.4.2
With plasma 5.5.2 I also cannot reproduce it anymore.