There has already been a fix for this that was done for performance reasons but should also fix your problem:
Though I will make a fix to the job so that it exits early if secure media is disabled.
Actually, I cannot do the above because we want post uploads to be marked not secure if secure media is disabled or if the post has been moved to a different category. Instead I will add a fix to capture the Aws::S3::Errors::NotImplemented error when we run Discourse.store.update_upload_ACL(self). That way clients that do not support the private ACLs should have no problem.
Edit: I merged this fix today, hopefully it will help FIX: Handle storage providers not implementing ACLs by martin-brennan · Pull Request #13675 · discourse/discourse · GitHub. I think we are cutting a new beta next week as well.