This article documents a particularly niche issue I ran into which took a
while to debug and resolve. I’ve posted it for the benefit of search engines,
so that the next person to run into these exact conditions might save
a few hours. You’re welcome.
This is probably interesting only to someone in my
exact situation, so most people should find some cat pictures to look
at instead.
If you’ve been directed here by a search engine because you’re tearing
your hair out, though, read on.