routing to user profile

In my multilingual site I need to link to user profiles from within my custom module. I set up a cb profile menu item in a hidden menu of type "Community Builder » userprofile" with the alias "users" and the Itemid=870. Now I take that link and refer to it in my module via SEF urls are set to ON in the Joomla configuration so the link generated looks in general like ".../users/username.html. But sometimes the userId gets inserted and the generated link looks like ".../users/xxx-username.html. What could cause that injection?

The user id is added if the username is not URL safe. See the below regarding how our new SEF rewriting works. You can use the Profile URL field to customize profile URLs even further. The username URL escaping uses Joomlas own alias function so the same rules that apply to a Joomla articles alias apply to usernames.

www.joomlapolis.com/blog/kyle/18704-seo-everything