NSO automatically detects out of sync-errors when contacting a device. NSO does not automatically do a periodic check-sync, but there a few ways of doing it:
You can use the build-in scheduler in NSO to perform the sync. This can be problematic from a performance point of view for short intervals and large number of devices.
If available on the devices, you can use an automatic mechanism such as the Netconf change-notification or an SNMP trap/inform to notice the change. This will require some implementation.
