Why would OnTriggerEnter get called, but not OnTriggerExit?

I have a stationary capsule collider with IsTrigger set to true and a character controller that rolls into the collider to display a GUI button. Neither has a rigid body attached. The documentation says that neither OnTriggerEnter nor OnTriggerExit should get called unless at least one object has a rigid body, but OnTriggerEnter is definitely getting called, while OnTriggerExit isn't.

Edit: C# script included below.

 void OnTriggerEnter(Collider collider)
 {
     WidgetStatus playerStatus = collider.GetComponent<WidgetStatus>();
     if (playerStatus == null)
     {
         return;
     }

     isTriggered = true;
 }

 void OnTriggerExit(Collider collider)
 {
     WidgetStatus playerStatus = collider.GetComponent<WidgetStatus>();
     if (playerStatus == null)
     {
         return;
     }

     isTriggered = false;
 }