It's hard to tell since you (sensibly) obfuscated your question but the way you've written it, I think this is a case of not naming the bucket correctly for this application.
sub.s3-website-eu-west-1.amazonaws.com
If the web site is "sub.example.com," then that's not the correct convention, so I wonder if your bucket name is also not correct: the bucket should be named "sub.example.com" -- not "sub" -- and the web site endpoint should be sub.example.com.s3-website-eu-west-1.amazonaws.com.
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