[BUG?] Album covers disappear on Create New Library

[jan_axhell]

Hi all,
I've been using MusicBee for about a month with extreme satisfaction.
At the beginning I've scanned everything I had and started tagging and importing Album Covers.
But since there was a lot of garbage I wanted to get rid of, and scanning Library again excluding those folders/files had no effect,
I decided to create a New Library from scratch paying attention to include only what I really wanted.

To my surprise, many, if not all the albums for which I had downloaded covers with "Embed picture in file" and "save to folder.jpg" flags ON,
disappeared. But they are there, the folders all contain folder.jpg and files show modification date coherent with the image. So MB actually downloaded and embedded them.

Again, if I right-click any of those albums and Send To -> File rescan all the covers reappear!
Why didn't MB find those in first place while importing to Library?

I have tried to "Scan folders for new files" in the hope it would see them, but it didn't happen.

Is there a way to mass-rescan the files instead of going inside each Artist profile and manually selecting them?

FYI I have not touched, nor changed paths in any way, the HDD is the same and I only unchecked the folders I didn't want to be imported.

EDIT: Found the Tools/Advanced/Rescan All Files function; launched now, will see in a couple of hours what happens. Nevertheless I think this shouldn't have been necessary in first place.

EDIT2: Nope, it didn't work. Disappeared covers stayed like that. I have randomly selected some to Send To > File rescan and they did reappear. Is this a bug?