Problem adding a tab to the user menu
The reason for your problem is that page manager has already defined a menu entry for that path. Just as well, because the menu item you have created would cause an infinite chain of redirection. You would need to change the path for your panels page to be something different in order for the redirection to work.

But you can simply remove your menu entry altogether and use page manager to define the menu item for the page as a tab under Settings -> Menu. You shouldn't need any extra code to do that.