I discovered the issue. Appears to have been some Media Reconnect issues FCP wasn’t letting me know about. I had all the source files backed up on an NTFS drive (originally on a mac OSX journaled drive). When I reconnected everything with the backup drive (same file/folder structure) apparently the narration stuff went AWOL – even though it appeared as connected and displayed waveforms.
I opened it today and it prompted me to reconnect and then everything worked fine. I had to click reconnect on the file in the timeline before it would work, but it played the audio just fine.
Thanks for the suggestions!
–Jon