Forticlient: Iphone6s switches from wifi to 4G

Hi,

I am using the Forticlient app (5.6.6.0194) on my Iphone6s (iOS 11.4.1) with an SSL-VPN setup with no split tunnel.

When using over home Wifi (WPA2-PSK) all works fine. At work however, WPA2-Enterprise, most of the time my Iphone immediately switches from wifi to 4G as soon as i turn on the VPN connection.

I already did all the obvious things i guess. Reinstall the app, restarted the iphone, rebuilt the VPN profile etc.

Has anyone seen this before?

Erik