Hello there, I'm Chris, a long-time .Net chap. I've been writing C# and using .Net since they were invented.
This looks straightforward enough, AutoFac, EF & SQL aren't going to be part of it, the solution will very likely be in your Net Core middleware and hosting environment, and in actuality probably isn't a problem as such, apart from the fact an exception is being thrown when building the response header, which slaps a spanner in the works from then on.
A bit of debug code should tease out what's going on, a bit of a pain to dig into since you say it's only happening in production and I guess that's part ofthe reason you're here. Not a problem, if you don't have anything built in to capture debug output we could add a webhook to have incriminating info squirted to Slack (would mean I didn't need to know your host login, say) or just log to a file etc.
I just registered here today, yours is the first job I've looked at. As such, I'm happy to quote low so I can get things moving on this site, start building a respectable profile and all that, drop me a line if you'd like me to sort this out for you.
Maybe it's not as straightforward as I think and if that's the case, I don't mind cheerfully doing the extra time to get to the bottom of it.
I am in Asia but have long since adjusted my day so UK office hours are when I'm at my desk, which means I work evenings essentially, I never was much good at early rising :)
Cheers, Chris