I believe this issue is on the same line as your other TTS issue.
Is this happening on this project only? The error and export thing?
Instead of Importing Library, try to copy sldies with audio to the other project and the export it from the other project?
You can definately export multiple audio files from Library, it basically can export to two comression forms MP3 and WAV.
and it is named as text to audio## (with number.)
Thanks,
Anjaneai