2 WAN Interfaces, only one default Route after reboot

Hi,
i have two WAN interfaces:
A) Get public IP by DHCP from a modem connected to eth2. Gateway Metric is set to 5.
B) Fixed private IP used with another NAT Router (Neighbours Fritzbox) connected to vlan 178 . This is my Backup Internet Connection. Metric is set to 10. So it will not be used.

When i look at the routing table after rebooting the omnia it looks like:

root@turris:~# route
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
default         ip-178-201-124- 0.0.0.0         UG    5      0        0 eth2
...

The second default route is missing. When i (re)connect the second wan if in luci the routing table is correct:

root@turris:~# route
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
default         ip-178-201-124- 0.0.0.0         UG    5      0        0 eth2
default         192.168.178.1   0.0.0.0         UG    10     0        0 eth1.178
...

Whats wrong here? I need both default routes for mwan. Reconnecting the second wan if after every reboot seems not to be a durable solution.

BR

mode

Any idea? Somebody with multiple WAN If can confirm this?