Forum OpenACS Development: Re: http POST X binary file
Certainly, ns_sets (which are used for header fields) can be reused within a request for multiple usages/purposes. After a request, these are cleaned up automatically via "ns_set cleanup". So, if you use/reuse e.g. an ns_set for headers for multiple "ns_http" client requests, and you are always adding additional fields to it, you might end up with a request with multiple "content-type" header fields. So, the general recommendation is to use always fresh ns_sets for http-client requests (unless you know, what you do).
I have no idea what possible be causing this strange behavior in my installation.
I've upgraded to NaviServer/4.99.19 (tar-4.99.19) and acs-kernel-5.10.0d30. last week. Plus it's a fresh install. So it's too recent to get myself "forking around" anything in the core
It could be NGINX cache. However, it happened only in this instance, among others, which are served by the same proxy.
Anyway, all it means is that I need more time to dig further into this problem and find the actual cause of it.