Any changes to a file, such as copying a file with the same file name, done from outside MB, such as dragging or copying from Explorer or changing tags, will require you the do a file rescan from within MB. Otherwise MB won't know that anything has changed.
At first thank you for the comments.
However your statement that MB won't know that anything has changed is NOT true.
When I drag a *.mp3 file onto a Playlist in MB then MB inserts the new song into the playlist.
BUT when MB inserts (=do) something means that it gets notified about an addition.
And when MB gets notified it could automatically append a file rescan.
Having to trigger it manually every time I drag a new file is tedious and leaves room for improvement :-)
So may I ask you to add an auto-rescan for every dragged file?