Use backup-stay-up only when there are no IP addresses defined at circuit level.
The backup-stay-up command should only be used in conjunction with VRRP addresses. This type of configuration is typical for Check Point VSX deployments.
virtual-router vrrp-id 20 circuit inside
ip 192.168.10.1/24 192.168.10.255
When using IP addresses configured at both circuit and VRRP level, the backup-stay-up has to be removed:
ip 192.168.10.2/24 192.168.10.255