You are having repetitive occurrences where the connection by ssh to the MGR site is not possible directly or from another server, although the ping is successful. Possibly, after a reboot on-site, the connection is established.
If you are on an unsupported software version (refer to the Product Bulletin for information), we highly recommend that you upgrade to the latest GA software release R19.2 with RHEL 7.9 so you can have several bug fixes and feature enhancements that were applied to RHEL.
You can reach out to your Account Manager directly via email to plan the software upgrade.
If the problem persists after the upgrade, please raise a support ticket including the /var/log/messages file containing the logs from the day when the problem occurred.
If the customer raises a ticket after upgrading to the latest software, elevate to the Professional Services team.