NSUrlSessionTask error: The network connection was lost (TLS issues?)

We are working on an update to our app and have noticed that some of our users have issues uploading data to certain endpoints.

This is the error:

Task <FBDD7D4D-E71F-41BE-84AF-DA94F090E6F7>.<1> finished with error [-1005] Error Domain=NSURLErrorDomain Code=-1005 "The network connection was lost." UserInfo={_kCFStreamErrorCodeKey=-4, _NSURLErrorFailingURLSessionTaskErrorKey=BackgroundUploadTask <FBDD7D4D-E71F-41BE-84AF-DA94F090E6F7>.<1>, _NSURLErrorRelatedURLSessionTaskErrorKey=(
"BackgroundUploadTask <FBDD7D4D-E71F-41BE-84AF-DA94F090E6F7>.<1>",
"LocalUploadTask <FBDD7D4D-E71F-41BE-84AF-DA94F090E6F7>.<1>"), NSLocalizedDescription=The network connection was lost., _kCFStreamErrorDomainKey=4, NSErrorFailingURLStringKey=<redacted>, NSErrorFailingURLKey=<redacted>}

Users who are using iOS 16.5.x do not exhibit these issues. However, uses on iOS 16.3 or 16.1 do exhibit these issues.

I was finally able to reproduce the issue by installing iOS 16.1 in the simulator and building the application and running it there.

Wireshark shows there are TCP retransmissions and then it closes the connection. It happens fairly quickly.

While using Charles proxy, it likewise fails. The "Failure" is:

Remote server closed the connection before sending response header

Building the same application on 16.5.x does not exhibit this issue.

I can confirm that Cloudflare says that the "client closed the connection" as I can see the TLS negotiation with Cloudflare. Subsequent requests don't even hit our servers. They just time out.

I'm totally lost here as while the code has changed between the 2 versions, the fact that it works on new versions but not on old versions seems to indicate a bug in the underlying library right?

I'm using AFNetworking here. This code is all Objective-C.