Facebook Messages : Instant Reply doesn't always work

We have Instant Reply ON for messages sent to our company page's inbox. But unfortunately, the Instant Reply only replies to 60-70% of incoming messages. On the other messages Instant Reply simply does not reply.

Once we notice it, we turn Instant Reply OFF and ON again. But there's no guarantee it will work the next time.

Does anyone have the same issue?

Any ideas why Instant Reply might be skipping work?

Thanks