Understanding the upgrade process on the Forticlient VPN client when using EMS

I have number of users on the 6.4.x client which I am upgrading to 7.0.8 (installer deployment built out already).

Here is the process as I understand it when using EMS:
*Existing 6.4 client.x will be removed by EMS
*User receives a prompt to restart now or later
*Reinstall takes place following restart

Some of my users will defer the restart and shutdown their machines at the end of the working day instead.

For some users they will get the new client installed after serveral minutes following a laptop power on the following day.

For others, they have to reboot several times before the install works.

In some cases, I have had to disable the endpoint from EMS management and delete the device from management. Then manually deploy the VPN client.

Can anyone advise is this is the correct behaviour and what the recommended troubleshooting steps would be?

Looked on the affected machines and could not work out where the re-install files are located given that once the older VPN is uninstalled and I presume communication with EMS would be lost somehow.