we're running HA cluster of FG 60F with firmware 7.0.8. WAN1 has a static ip address from the ISP via bridge modem, WAN2 is connected to a FritzBox with a sim card creating a NAT (using a private ip address 172.31.1.0/24). When WAN2 comes online it causes WAN1's ip address to become unreachable (the interface is physically up).
There is no conflict in the static routes and policies. Can this setup even work or should we try to put WAN2 into PPPoE state?