I am using sample http_server and found that if I post to a URL with dynamic context, the first time I get a packet with a header and if I post again without waiting for client timeout, I don't get a header.
Log with additional messages added to show what header is sent:

I've added a line client->http1_header_sent = false when status is HTTP_SERVER_DATA_FINAL to fix the issue, but I don't think that is a good fix.
I am using zephyr commit 5305aa6