Load-balancing not working as expected

Hi all,

I am running an EdgeRouter Lite v1.9.1 in a dual-WAN setup. Load-balancing is configured to use `WAN` on `eth0` as default and `WAN 2` on `eth1` as failover-only. The setup is working fine so far.

However, for a bunch of devices I wanted to inverse the logic (`eth1` as default, `eth0` as failover-only). I started by creating a new group and modifying the route for selected traffic:

configure
set load-balance group DSL interface eth1
set firewall modify balance rule 60 action modify
set firewall modify balance rule 60 source address 192.168.1.100
set firewall modify balance rule 60 modify lb-group DSL
commit

So far this works as expected, traffic from `192.168.1.100` gets now routed via `eth1`. The next step was to add the `eth0` interface to my `DSL` group:

configure
set load-balance group DSL interface eth0
commit

Both interfaces now have a weight of 50% (as can be checked with `show load-balance status`). I also tested this via `curl ifconfig.me` which now randomly shows one of my two WAN IPs. Still nothing particular.

Next I tried to configure `eth0` as failover-only:

configure
set load-balance group DSL interface eth0 failover-only
commit

A `show load-balance status` displays the expected output:

Group DSL
  interface   : eth1
  carrier     : up
  status      : active
  gateway     : 192.168.188.1
  route table : 203
  weight      : 100%
  flows
      WAN Out : 28
      WAN In  : 0
    Local Out : 0

  interface   : eth0
  carrier     : up
  status      : failover
  gateway     : 192.168.178.1
  route table : 204
  weight      : 0%
  flows
      WAN Out : 25
      WAN In  : 0
    Local Out : 0

However, the `curl ifconfig.me` (or any other tests to check my public WAN IP) command now always returns the WAN IP of `eth0` and not `eth1` as expected. This surprised me as the 50/50 weight setup worked as expected a few seconds ago.

Did I miss something? Or does anyone experience a similar behaviour? I appreciate your support.

Cheers
Phil