@agileox. Thanks for posting. From your description, the module, as well as ACL on the module, works as expected.
The question is what do you want to restrict access on?
1. If you restrict access on the module, the module will only show for the user group that it was restricted to.
2. If you restrict access on an article (that contains the module), the article will only show for the user group that it was restricted to.
Let’s say the access level for the Module is set to “Registered” and and the access level for the article that contains the module is set to “Public”, then any user can see the article, but only registered users will see the module on the article page. Public users will not see the module on the article page. They will only see Public content. From what you explain, this is what you have set up.
On the other hand, if you set the access level for the Module to “Registered” and you also set the access level for the article to “Registered”, then only registered users will see the article with the module. Public, or guest, users won’t even see the article link at all.
This is how Joomla works. It isn’t unique to my modules. Hope this helps. If you need any further clarification, let me know.