Persisting the image (e.g. never deleting it) does not result in the error above, and runs a fully encrypted, 32-bit mySQL server.
This problem seems to only exist if the host machine is on a 32-bit architecture. Updating the OS image to 64-bit works, per comments with similar users.
After running the markdowns again on a 64-bit host machine (docker build .), we run into a problem. Image attached.
2a. Ongoing research in separate branch:
Using library/mysql:latest from official Docker repository on 64-bit architecture for now (minimal path).
After deleting and rebuilding this Docker image, i386/mysql:latest container never runs.