copy  any url from odoo 11 sitemap.xml, then try:

$ wget https://example.com/shop/product/schraube-92840 
[...]
HTTP request sent, awaiting response... 301 MOVED PERMANENTLY 
Location: http://example.com/shop/product/sz-09117-08047-000-schraube-92840 [following] 

This first step redirects from https to http and inserts the default_code (or internal reference) into the url.

Location: https://example.com/shop/product/sz-09117-08047-000-schraube-92840 [following]

This second redirect seems to be the proxy, which redirects every http request to https.

How to get a correct url including https and default code into the sitemap?