When localization changes, UIPopupList.OnLocalize will be called, which calls TriggerCallbacks(), which in turn sets the UIPopupList.current value and notifies all listener delegates. The only time UIPopupList.current.value is valid, is during the TriggerCallbacks() function call. If you have your code do your own localization and try to get the popup list's value inside, it won't work anymore as the value is not going to be valid.