Correct. After spending many hours on this and after analysing your LOG files, I came to the conclusion that there were NO 404 errors. All SetupBuilder Web Installation GET requests succeeded!
Well, the good news for you is, that you do not have a server problem. And the good news for us is, there is no SetupBuilder Web Installer problem.
This download came from IP 185.220.70.152. It's listed several times in abuse and spam databases.
This download came from IP 178.62.228.82 and belongs to Digital Ocean in Amsterdam, The Netherlands. I bet it's some kind of spider-bot.
This download came from IP 66.102.6.183 and belongs to Google LLC.
This download came from IP 35.161.55.221 which belongs to Amazon.com Inc (amazonaws.com) and it's listed in abuse and spam databases.
To cut a long story short, all mentioned "downloads" stopped with code 200 because "The Machines" simply terminated (killed) the sandbox executed Web Installations after a specific number of downloaded cluster files. There were no human beings behind the downloads. All Web Installs "stopped/terminated" intentionally.
Friedrich