Acess control not working when assigning roles tag or category

Hi, I love your plugin ( version 1.3.88 ) but the access restriction is not working when assigning roles to tags or categories. But it works when assigning roles to a specific post. This is probably due to the set of parameters I am using for my site.
I can read and understand PHP code. If you let me know where in the plugin ( file name and line number ) the test is performed for selecting posts for the current user on the basis of the roles assigned to their tags and category, I might understand why it does not work for me.
Thank you for your help.