I have loade 3 albums to my shared NAS folder and done a rescans and updates but I see this albul with a question mark which corresponds to nothing. There are no tracks. The settings>Sources indicates 4 albums. I can’t seem to get rid of it.
Thanks
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Suggestion : check if you don’t have an hidden .bin folder. Windows move deleted files in it, but still here 
The Synology Nas is runnig Linux but it did recreate a recycle folder(again). Deleting it solved the problem .
I think there is a way of preventing the creation of a recycle folder but I can’t find it.
Found it:
Control Panel → Shared Folder → [Folder] → ‘Edit’ button → Uncheck 'Enable Recycle
