Attempted with jsreport.Client, I get the 404 error.
Attempted with custom, It downloads the file
I bet its something silly on my end but cant for heaven's sake figure it out :'D .
For now I have gone ahead with the custom implementation. A voice in my head keeps wanting me to figure out the cause of this error :D If you want to get to the bottom of this error as well, I can put in a request for a test user and set up a mirror report and DM you the details.