I believe I may have a fix for the issue, which appears to stem from a bug in unix pathname conversion for shadow copies. If you are willing to test the fix, please email me at awalker@ixsystems.com.
The following system core files were found: smbd.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 Once the core files have been archived and attached to the ticket, they may be removed by running the following command in shell: 'rm /var/db/system/cores/*'.
13.0 PR: https://github.com/truenas/ports/pull/1024