David Bremner <david@tethera.net> writes:

>
> Thanks for the report. I don't yet understand where the bug is, but I
> think it's safe to say it's not in your code. I made a somewhat simpler
> test case that displays the same problem (at the end).
>

Oops, I cleverly wiped out my modified test case test-unpacking the
attachment. Luckily I still had it in a buffer. Here it is