Dual wan with USB works fine. Dual wan using wan and lan1 or any other lan port is broken if configured to load balance. I'm unsure about failover as that's not my desired configuration. I'm using an RT-AC66U B1 with the 68U firmware. It could possibly be an issue connecting to SSL websites. I can ping google or reddit or any other site that responds without issues however most sites hang at "establishing secure connection" in the browser. Tracert also only goes to the router and then a single hop before it times out. The instant I disable dual wan the issues goes away. The issues do not occur on my RT-N66U, dual wan works perfectly.