When CPE is being staged, "Transport Timeout/Closed" Error displayed while post-staging template is being applied, Despite good end to end transport
Below config tweak might help to overcome the issue incase the CPE template config is huge and ultimately it may time out before even completing the config push to the CPE.
Versa-Director-1% set devices global-settings read-timeout 600
Versa-Director-1% set devices global-settings write-timeout 600
Versa-Director-1% commit