Did you replace nethesis-test with the name of your IPSEC VPN?
The second line should be: (changed from NS6 to NS7)
signal-event nethserver-ipsec-tunnels-save
This error occured in this thread too.
To get the custom properties as shown here: (I assumed 192.168.8.1 is the Nethserver green interface)
db vpn setprop <YOUR_IPSEC_VPN> Custom_aggrmode yes Custom_left %defaultroute Custom_leftnexthop %defaultroute Custom_leftsourceip 192.168.8.1
signal-event nethserver-ipsec-tunnels-save
For more information about the ipsec options you may have a look at the ipsec.conf manpage.