S3 backup on Hitachi HCP

I’ve struggled with S3 backups on Hitachi HCP for a while.
I’ve narrowed it down to the client.SetCustomTransport(tr) in rke-tools.
Is there a way of debugging the http.DefaultTransport? or tweek the configuration?
removing the client.SetCustomTransport(tr) statement makes it work.
All I know is that the HCP returns transport-encoding: chunked and I think that might be an issue (when comparing to AWS S3 or minio)

br hw