Wrong gateway (lower tier) used as default gw in Gateway Group

[soupdiver]

I try to configure a multi WAN setup. I have 2 uplinks.
I created a Gateway Group and set my preferred interface to Tier 1 and the other one to Tier 2.
As the default gateway fro ipv4 I set the Gateway Group.

After saving (and rebooting) I can see that always the wrong interface is used as default gateway. The one that has Tier 2.

Did I miss something?