I am facing issues with my auto-renewing subscription for an iOS app that offers auto-renewable subscription. The Subscription Status URL is at times, not being called when the subscription is renewed. This is making it difficult for us to track the user's subscription status. Funnily, this behaviour is completely arbitrary at times it is called and everything works smoothly, but at times it is not called at all.
Also, once the user's subscription is renewed, at times the user is not charged on his/her credit card instantly. Is this behaviour normal?