CRM 2013 Xrm.Page.ui.navigation.items.get("---").setVisible(true) not working ?

Hi There.

In one of my CRM 2013 projects, the setVisible function seems not working properly when it is triggered by a OptionSet value change and setVisible(true). The code is triggered but the navigation item is not showing

Anyone else has experienced such behaviour?

Xrm.Page.ui.navigation.items.get("navActivities").setVisible(false);
Xrm.Page.ui.navigation.items.get("navActivities").getVisible(); //return false
Xrm.Page.ui.navigation.items.get("navActivities").setVisible(true);
Xrm.Page.ui.navigation.items.get("navActivities").getVisible(); //return false again

Regards,

Jaimie