When you assign a shortcut (for instance WIN+E to open Thunar) using the WIN key, every time the shortcut is used the menu is shown. The menu should appear only when the WIN key is pressed in isolation. Thank you.
This is a known issue with the Xfce keyboard shortcuts. The shortcut to show Whisker Menu is not actually handled by Whisker Menu, so there is nothing I can do. Sorry. *** This bug has been marked as a duplicate of bug 7845 ***
Thank you for the link to the bug, I did try searching before, but I couldn't find it.