FortiClient - no_dns_registration issue

Hello, we use FortiClientVPN (free) for VPN SSL and we want to registers the VPN tunnel interface IP address only in our DNS server. This is achieved by setting the FortiClient config xml value "no_dns_registration" to 2 (https://docs.fortinet.com...guide/858086/ssl-vpn). Doing the above, when a remote user connect to SSL VPN, FortiClient clear the flag on Windows Networking for IPv4 DNS "Register this connection in DNS" on the phisical Ethernet/Wifi adapter, and that's exactly what we want. The issue occurs when the user disconnect from VPN SSL, Forticlient do not revert the flag to the original setting. We are using the latest version of FortiClient VPN software for Windows, that as to date is 6.4.2.1580. Anyone has noticed this issue? Thank you, Matteo