(Fixed formatting -- please use preview.)
If I understand correctly you have two layers: a frontend (nginx) that dispatches to a backend (apache+mod_wsgi). This is a very common setup and you don't need FORCE_SCRIPT_NAME
to make it work properly.
I don't understand your second comment: I don't see anything related to urlparse in build_absolute_uri.
Generally speaking, the information you've provided is rather sparse, and we have evidence that the admin works for thousands of developers using the same setup as you.
This looks like a misconfiguration. I suggest using the support channels.