Hi Michael,
Thanks so much for your suggestion. It’s not actually showing a Drive path for the audio only clips, which I think suggests what I suspect – that the audio clips were Linked To, not Imported. I did try a Batch Import previously, but to no avail.
I feel like there should be some sort of Decompose / Unlink / Relink workflow that would do the job; I just can’t figure it out completely…
Nick