Problem with Dual WAN after upgrade to 5.6.3

Hello from Austria,

I have a weired problem, maybe someone has a hint for me:

We're using a 92D:

On WAN1 is a broadband line with DHCP for the transport IP and a /29 subnet routed over this transport IP.

On WAN2 is a DSL with PPPoE authentication, I also get a transport IP and have a /29 subnet.

The guy who mostly managed the firewall has somehow configured a failover, so if WAN1 is down, all traffic gets divertet to WAN2. As he is no longer available, I cannot ask him, how exactly he has configured this, because there is no SDWAN config and also no link monitor configuration. I just realized, that it somehow worked.

Both Interfaces have the distance 5 and as both default gateways are aquired with DHCP, I cannot manage the priority.

Everything was fine until today I upgraded from 5.6.2 to 5.6.3. After the upgrade the default route is pointing to WAN2 and I have no idea how to switch back to WAN1. I tried to lower the distance to 1, but that didn't help.

In the routing monitor I see the trasport IP and the default gateway from WAN1. When tracerounting to the gateway-IP, it's reached in one hop.

And now I'm very clueless where to look next resp. what to do to get the traffic back to WAN1.

Any help highly appreciated.

Thanks a lot,

William