There is a bug in Rekordbox versions 5.6.1 and above that causes any tracks imported from Rekordbox XML that already exist in the library to not be updated. This includes Rekordbox 6.*
When importing tracks from Rekordbox XML, normally any tracks that are already in the library would be overwritten with the newly imported version, however, this bug causes that to not happen to leave the track in its old state.
There are a couple of ways to work around this. The first is to use version 5.6.0 or earlier where this bug doesn't happen.
The second workaround is to first right-click a playlist and select "Import To Collection". This will only import tracks that were not already in your collection.
Now, select all the tracks in your playlist on the XML tab (CTRL+A or CMD+A), right-click and select "Import To Collection".
This will force Rekordbox to import all these tracks and overwrite them.
