I assume you have tried the obvious thing of selecting the other whisper options as well? Do any of the other options change the roll? If you check the attributes tab of the character journal, you should see an attribute called "wtype". The value of wtype dictates how whispers are handled. You should see the value of wtype change as you change the whisper setting. If you don't see the value change, I would delete "wtype". Don't worry, it will be recreated by the sheet as it's needed.