No-one had responded so I had a look to see if I could find anything. Most were after stapedectomy, which did not answer your question.
I found this in ResearchGate:
Chrobok, V., Jezek, B., Simakova, E., & Cerny, M. (2011). Facial Canal Dehiscence and Prolapse of the Facial Nerve-Case Reports. CESKA A SLOVENSKA NEUROLOGIE A NEUROCHIRURGIE, 74(4), 478-481.
Article Facial Canal Dehiscence and Prolapse of the Facial Nerve - C...
This might also be relevant; the RG link does not have the full text:
Wu, C. M., Ng, S. H., & Liu, T. C. (2008). Facial Nerve Overlying Stapes Footplate as a Cause of Conductive Hearing Loss. Otology & Neurotology, 29(8), 1204.
Article Facial Nerve Overlying Stapes Footplate as a Cause of Conduc...