Timeout issues and app dying


I'm encountering some weird problems with our Kibana installation.
When the app is running, I sometimes receive Timeout errors from the Discover page saying the 30000ms timeout is exceeded. (they appear faster then 30 seconds, not sure what's even there)

After a while, Kibana just dies completely returning Timeout errors in Firefox.

We use daily indeces on our ES in the back-end, and they're not abnormal large.
I think our largest index is around 10GB?
And we have a daily cron-job running that deletes indeces older then 7 days from ES.

Is there anything I can do for more information, because this problem keeps happening on irregular basis and is really making the application useless at the moment.

Hm, I'm not sure why an error message would show up before 30 seconds passes.

Is the index pattern loaded into Kibana using the optimized option for time-based events, as opposed to the deprecated option where event times create index names?

I've checked the settings of the patterns, and they are set using the index contains time based events and the one with [DEPRECATED] is not checked.