NaZz Wrote:
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> If its unrelated to nginx why are people suggesting to edit various
> settings in nginx.conf to fix this particular problem?

You can only do so much with config, the real problem here is the upstream (=backend).
nginx talks English <> your backend talks Russian
Somewhere your backend started talking a Russian dialect nginx don't understand, hence the need to fix your backend.

The hint " upstream sent invalid status " should say enough.

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