The file “***.fcpxml” could not be imported. An unexpected error occurred in importing the media.

Open the XML with a text editor.

Search for the first occurrence of "<resources>" - resources[1]

From there search for the second occurrence of "<asset " - asset[2]

There you will find the path URL for the file "src="

Check this file.

If the file in the library isn't an alias, what exactly is it? If it's the file, will the file play in the QuickTime player, and what are its specs?

If you've changed the contents of the library bundle you might have damaged it. With the application closed try deleting the flexolibrary file from the bundle and reopening the library.

What if you URL encode the file path like it is for Library location? (adding %20 for spaces)

file:///Volumes/OTHER/Evenant%20-%20Ebook/AUDIO/KP%20-%20Evenant%20-%20TSS%20Out%20Of%20Sight%20Dialog%20(De%20Noised).wav

The duration can’t be zero. The whole string of clips that are used are likely missing.

Do you know where the file is? Is it on your system drive or an external drive? Can the Finder locate it?

Save all the data, start/end/duration in case you have to rebuild the edits.

You also may try this:

Create a new library and close all others.

Create a new project.

Import your .wav file and drag it to the project.

Export as XML.

Open the XML in a text editor as described above.

Now as the file is the only asset it's easy to find it (and to get all it's attributes).

Copy the "<asset ... " line – it ends at the first "/>" after the "<asset ".

Now open the 'bad xml' and locate the 'bad line' same way.

Paste the 'good line' before or after the 'bad one' – doesn't matter.

In the 'bad line' there is a so called attribute 'id' – 'id="r6"' in you case. This id will be used throughout the XML as a so called 'reference'.

Copy that 'id' and replace the matching part of the 'good line' with it.

Now delete the 'bad line'.

Just for security create another library and close the intermediate one.

Import the XML.

In case everything works consolidate.