We have a large number of subscriptions to /users/<userID>/messages with different user ids.

At some point the service stops receiving notifications for some of the subscriptions even though there is an activity in mailbox.
This only happens to a small subset subscriptions.

Attempts to extend the expiry time of the subscriptions succeed without issues to those subscriptions.

Creating a new subscription does not help (without deleting the old one).

Is there a way to fix these subscriptions?

Is there a way to detect when subscription stops working?

Is there a way to avoid this situation or to fix one when it happens?

Would deletion of the old subscription before creating a new one help?(this isn’t trivial to test right now for us)