Jira is getting down approximately after 4 hours with latest version 8.18 upgrade

Hi Guys,

Recently we have upgraded Jira software version to v8.18 for compatibility and approximately after 4 hours, whole Jira became un-responding. We have observed CPU, Memory and thread dumps, nothing found.
We have observed this pattern multiple times and every time it went un-responding after 4 hours.

Is there any thing wrong with Jira version 8.18 or with our App ?

Awaiting for answer. Thanks.