Hi there,
Thankyou for reporting.
Whereas copy+paste audio prototype functionality is purposely designed. You can't copy-paste the audio prototype to other document. But you can make a component with audio prototype and publish that document, so you can use that assets anywhere from library.
I hope it will be helpful . Please let us know for any confusion.
While saving existing files with audios in it , works fine from our end.
Would you tell us, which version of Xd you are using ?
What audio formats are ?
Window Os version ?
Regards,
Anita Subedi