Clients loosing configuration group

Hi,

we are experiencing a strange issue on SEP Managed clients. 

To allow some of them to connect through VPN, we have moved them (from the console) from the standard group to a dedicated one. 

All is working correctly, they get teh new policy and own to the new group, until they (after some days ) come back to the office and connect to the LAN. In this case they are moved back to the original group.

Seems like the client are deleted ( due to the secting of deleting clients not connecting for 30 days ) but when they connect back to the server, they are back to the original group, no to the last one.

Does this make sense? Is there a way to avoid this without removing the 30 days deletion?

Thanks,
Mirko