Just noticed the same leftover menu shadow when, from Podcasts, one selects "Edit -> Podcasts -> Export subscribed podcasts" as well.

Yes. But the behavior doesn't change if I activate the same menu command several times in a row.

Would that be the menu previously shown?

Added as: https://www.ventismedia.com/mantis/view.php?id=19541

I noticed a black box remain on the screen when I chose File - Export - Export Subscribed Podcasts.
This is using the new 5.0.4.2682 beta.

Windows 10 Home edition