Client machines require a restart after updating printer driver to v2018.3 Follow
When updating from a driver v7.4.3 or older on a network, the client computers will require a restart before they can pull the new driver from the print server
This problem is caused by the difference in printer certificates used in each version. Version 2018.3 had a new certificate generated for it (so that it wouldn't be expired in the new release) and Windows seems to take longer to recognize this server-side. This forces the clients to require a restart to update.
If you install the certificates first before the upgrade, no restart is required. Else the only fix is to restart the clients.
Please see this article about extracting certificates from our drivers: Installing Authenticode signature prior to Seagull Driver installation
This is an unfixable issue as it deals with Windows. Please see this JIRA for more information: https://seagull/jira/browse/DRV-3340