We've encountered a few periods of Facebook messaging API high failure rate during the last 12 hours. Unfortunately, according to our studies, some of messages failed to get to subscribers even being successfully sent.
The problem was global and all the Messenger Platform was affected. We still don't know the reason of the issue & are trying to get more info on that right now.
Now, all bots seem to be working properly according to our tests & metrics. We advise you to check your campaigns & bot's conversations to make sure your customers got everything they needed from your Messenger bot.
We'll continue monitoring the platform & will notify you if we see something going wrong again.