We have several RV042's set to failover mode.  None of the will switch back to the primary WAN interface once the internet has come back on for that interface.  Is there a setting I'm missing somewhere?

I have a RV042 using (for now), just the single WAN interface. I am trying to forward all packets to port 9000 from the WAN to a single IP address on the network.  I've set up both forwarding rules under Setup -> Forwarding and under the Firewall -> ...