With the introduction of CWF in SQL Safe 9.3, previous agent versions that do not include the CWF changes are no longer supported in a mixed version environment.
Previously, you could upgrade the management service while still using older agent versions, but now, upgrading the management service will prevent communication with those prior agent versions, as they do not use the new CWF protocols.
Older agents will still process backups but their statuses will not be sent to the management console. To help with agent upgrades, SQL Safe provides a mass upgrade wizard to simplify the process.
If you choose not to upgrade all agents, we recommend creating a new application server for SQL Safe 9.3 and split your assets across version 9.3 and older versions.