Using web page runner and chunked response

Beginners question: I set up a simple web load test with a web page runner and a fixed rate generator. The workspace runs in local mode. I call a localhost URL with a parameter. Passing to the host is done correctly. The response to the request has transfer-encoding chunked. No matter how many requests I set up, most (above 90%, and I do not trust the others) are shown as failed.

Any idea what I am doing wrong?