Okay, I thought a bit more about the possible differences…
- Both sites ran the same version of Discourse.
- Both sites temporarily ran the exact same set of plugins for testing.
- The site settings in the
Oneboxcategory are identical. - The site settings in the
Basic Setupcategory are identical. - The remaining site settings are not identical, but no difference seems related to oneboxing.
- The language settings in
app.ymlare identical. - Both sites run under a nginx proxy handling SSL.
- Both sites are non-subfolder-installs.
- Of course, both sites are supported Docker installs.
- Both sites are running on Ubuntu 14.
Some differences:
- The site with the broken Oneboxes failed the automatic upgrade to Postgres 9.5.
- The site with the broken Oneboxes is running on a fourth-level domain; the other one is running on a third-level domain.
I’m not sure whether local oneboxes have ever been working in the broken instance.