Uplink Balancing & NAT Masq
Problem: You may create NAT Masq rules for your ISP and segment off portions of your network to specific addresses under Network Protection > NAT. If you obtain a secondary ISP and turn on uplink balancing under Interfaces & Routing > Uplink Balancing, your NAT MASQ rules change to uplink interfaces. The NAT MASQ rules only MASQ the primary interface. The current interface doesn't allow for changing to multiple interfaces.
Solution: Allow uplink balancing to be used and allow multiple interfaces to be configured under the MASQ ruleset so that traffic may use either configured interface to NAT MASQ.