SSL VPN and IPSec VPN interfere

[zoneless]

Hi.  I am fairly new to Fortigate and am trying to configure a Fortigate 100E, currently on 5.4.7.

I followed the cookbook guide for SSL VPN (http://cookbook.fortinet.com/ssl-vpn-using-web-and-tunnel-mode-54/) on WAN1.  Multiple colleagues could connect using FortiClient and everyone was happy.

Then I am trying to add IPSec VPN for iOS and Android using their native connectors (following http://cookbook.fortinet.com/ipsec-vpn-for-ios-devices/ and similarly for Android) on WAN2, using different IP ranges.  I could also get multiple devices connected.

A problem occurs though when my colleagues are connected in office with FortiClient, and then somebody tries to connect (or disconnect) their VPN on iOS or Android, all the FortiClient connections would go down.

Is there any added configurations to the cookbook's I need to do for my setup?