Dual wan is partially broken in newer firmwares

[dezents]

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.

 

[brummygit]

I've been struggling with Dual WAN failover recently using WAN with LAN1 connected to a 4G router. My problems seem to be around detecting the connection state and related to the use of DHCP and/or Static IP on the secondary router. I think I have stabilised it on Merlin 384.19b1 at the moment by using DHCP for my 4G router but with manually configured DNS servers, however I need to double check as it seems to work one day but not the next.

Symptom's I've seen were LAN1 remaining in Cold Standby when configured as Static IP, and when using DHCP I was seeing failover to backup and but that caused the router to incorrectly detect that the WAN circuit was back up so it failed back every couple of minutes before starting the cycle again.

 

[Chuckles67]

I played with Dual WAN failover using WAN and LAN4 on same router as dezents, with Merlin 384.18. I saw the internet was disconnected on devices with WAN (docsis modem), and soon gave up.
My current setup is Dual WAN failover using WAN and USB, and WAN internet works as expected, so agree with the original post something seems not right here.