REST API POST error response is in unreadable format

Can you please help me understand why such response is received.

we are using standard oracle process to read the response:

 IF p_wallet_path IS NOT NULL AND p_wallet_password IS NOT NULL THEN
    UTL_HTTP.set_wallet('file:' || p_wallet_path, p_wallet_password);
  END IF;

  -- Initialize the CLOB.
  DBMS_LOB.createtemporary(l_clob, FALSE);

  -- Make a HTTP request and get the response.
  l_http_request  := UTL_HTTP.begin_request(p_url);

  -- Use basic authentication if required.
  IF p_username IS NOT NULL AND p_password IS NOT NULL THEN
    UTL_HTTP.set_authentication(l_http_request, p_username, p_password);
  END IF;

  l_http_response := UTL_HTTP.get_response(l_http_request);

  -- Copy the response into the CLOB.
  BEGIN
    LOOP
      UTL_HTTP.read_text(l_http_response, l_text, 32766);