When I run minio upstream from nginx, Duplicati complains about size (RequestEntityTooLarge). I added (as per minio documentation) proxy_buffering off; but nginx complains nginx: [emerg] invalid value "proxy_buffering". Can someone help?
Silly me, it was client_max_body_size 1000m; (and I knew that) and the error came from a missing ; (weird error message)
Glad you figured it out!
I realize this is not exactly related to your issue (and I can’t find the post right now) but I think somebody else ran into a similar error when some unrelated development cookies got passed into the Duplicati UI.