Upgraded to Truenas 12.0 yesterday. Realized that there is a message to upload a core-dump:
The following system core files were found: sshd.core. Please create a ticket at https://jira.ixsystems.com/ and attach the relevant core files along with a system debug. Once the core files have been archived and attached to the ticket, they may be removed by running the following command in shell: 'rm /var/db/system/cores/*'.
2021-03-25 17:33:31 (Europe/Berlin)
I am not sure if this was raised during a reboot of the system, but anyhow - if it improves the system, i follow the guidline ;)
Hope it helps.