Business Rules not executing

Hi,

I have written Business Rules which executes on the Close phase of Business Process Flow. There is an option set on the close phase, when a specific value is selected in the option set, i am displaying/hiding few other fields which are also on the close phase of the Business Process Flow. The problem is, When the option set value is changed, sometimes the Business Rules executes and not every time. I need to deactivate the Business Rule and reactivate it again. I will work for some time, then again the option set will not display/hide other fields. Can someone please help ?

Thanks

Najm