Instance stuck in Stopping state.

Alright just got it to stopped state and restarted it. Still our server was down for ~30 minutes, which aggravated some of our clients.

Hi there,
There was unexpected underlying hardware issue and to recover the instance, I see you have stopped and started it. I'm glad to see that the instance is up and running now.

You can set up alarm which gets triggered when such issue happens and you can take necessary actions but the there is no way to know in advance when the issue would happen unless this is planned maintenance / retirement.

Status Check Alarms:
[+] https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/monitoring-system-instance-status-check.html#creating_status_check_alarms
[+] https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/UsingAlarmActions.html

I hope this helps.
If you have any further queries, please let us know.