When you select ALB mode in the web UI and reset the network everything appears to function properly, but you notice two issues:
1) The second NIC may appear as offline in the web UI
2) There is an assertion error and subsequent memory dump in the syslog.
Both of these conditions are cosmetic. If you run the ethtool on either network port you will see that both nics report a link and ifconfig shows that they are active and transmitting data.
The issue has been resolved in GuardianOS 5.1.046 and later versions. Please upgrade the system to resolve this issue.