I think I found a bug that only exists in 8.1.1
If you enable IP Passthru and disable the 192.168.50.10 DHCP server, the device connected to LAN1 gets the public IP etc.
However, it can no longer has internet access.
Also, Incontrol2 loses all access to the device and sees it offline.
This setup works perfect in 8.1.0
I just verified that downgrading to 8.1.0 fixes the issue.