Buurst recommends the best practice of creating a snapshot of your current machine image state before applying any updates. This should allow you to roll back to our previous SoftNAS configuration/version by restoring the snapshot if necessary. The below links will help you to create the required snapshots.
SoftNAS Snapshot Documentation
SoftNAS Recommended Best Practices for Maximum Data Protection
Snapshots in StorageCenter
Location of Snapshot files
For VMware and Veeam: