2.4 Gateway Groups?
I have a gateway group that includes my ISP gateway plus an OpenVPN gateway. I created a simple gateway group that puts the OpenVPN gateway as Tier1 and my ISP gateway as Tier2.
Everything works great, until the OpenVPN gateway goes offline. Once that happens, my traffic fails over to my Tier2 (ISP) gateway, but if my OpenVPN gateway is brought back online, traffic never fails back to Tier1.
It appears after a reboot, traffic is still sent out Tier2.
I have a different issue with gateway groups and failover, but you should check to see if Sticky Connections is enabled… It will retain the gateway in use for all past and current connections. Future ones should revert to highest tier though. You could always try resetting the state table after Tier 1 comes back up as a test, it should assign to highest tier at that point.