WAN down, but LAN will not failover to Backup FW

[robert1157]

Hi,
we are currently adding a second firewall to our setup for HA.

While testing we saw that, when we disconnect the WAN port on the primary FW, the VIPs on the WAN Interfaces fail over to the secondary FW, but nothing happens on the other interfaces (LAN, DMZ, etc).

We are using the Netgate 1541 as hardware platform, copied the config from our old FW, changed the interface (on both), setup HA.
Config sync is working, state sync is working, CARP is working independently on the interfaces.

I have found this:
A similar problem (but in a VM): https://forum.netgate.com/topic/185613/wan-link-unplugged-but-lan-not-failoverto-backup
A similar problem (on older HW): https://www.reddit.com/r/PFSENSE/comments/dsbrbm/failover_issue_with_ha_setup/

Hardware / Software:

IP Config secondary:

CARP Status on primary and secondary:

After disconnect IP Config primary:

After disconnect - CARP Status on primary and secondary:

What could be the problem?
THX Robert