HTTP portal with the NTLM auth flow is broken on XC.

We are trying to protect an OWA365 portal with XC, but some requests with NTLM authentication show an Error 503 - Service Unavailable message in XC.

I think that is the NTLM auth process because when try the same HTTP GET with "Authorization: Basic" it works fine.

curl -v https://autodiscover.example.com/autodiscover/autodiscover.xml -H "Authorization: Basic ZG9tYWluXHVzZXI6UHJ1ZWJhc2RlcGFzc3dvcmQ="

< HTTP/2 200
< cache-control: private
< content-type: text/xml; charset=utf-8
< request-id: 00000000-0000-0000-0000-000000000000
< server: volt-adc
<
<?xml version="1.0" encoding="utf-8"?>
<Autodiscover xmlns="http://schemas.microsoft.com/exchange/autodiscover/responseschema/2006">
  <Response>
    <Error Time="20:00:00.0000000" Id="000000000">

But the browser always fails. First, it responds with a 401 HTTP code. After sending the credentials, XC shows a 503-03 error: 'Service unavailable'.

method: GET
host: autodiscover.example.com
req_path: /autodiscover/autodiscover.xml
req_body: —
api_endpoint: UNKNOWN
scheme: https
rsp_code: 503
rsp_code_details: upstream_reset_before_response_started{remote_reset}

Do F5-XC have an OWA template or something about the NTLM user portal?