I had a quick look in the logs (annoying the Kibana logs are both not very useful without changing the config and not accessible to ESS customers - both things we're actively working on) and the only thing I could see was all shards failed: [exception] Trying to create too many scroll contexts. Must be less than or equal to: [1024]. This limit can be set by changing the [search.max_open_scroll_context] setting.
- is it possible you were using some really heavy Kibana activity (can't imagine what it could have been) and it brought the service down? I see it's now happy after increase in number of zones and capacity
Anyway if you see the problem again, create a support ticket as above, and an admin can add the extra logging params and see if that gives more insight into the underlying issue