AC68U merlin 384.6, cant set failover.

[Payam Nab]

I have 2 cable networks and want use one as failover.
These are my settings:

Primary WAN: WAN
Secondary WAN: LAN 4 
Dual WAN Mode failover with Allow failback
Detect Interval 5 seconds
Failover Execution Time: Continuous 12 times (60  seconds) detect network failed
Failback Execution Time: Continous detect Primary WAN successfully over  times ( = 10  seconds).
Enable Ping to Internet: Yes
Target: 8.8.8.8

I dont want to leave the connection stay on WAN 2 after switch as its a metered connection.
Problem is when WAN 1 lose network connectivity and there is no ping it switches to WAN 2, but then it ping 8.8.8.8 from WAN 2 and switches back to WAN1, while WAN 1 has no connection.
Tried to set the ping address to WAN 1 external static ip address, but then when it connected to wan 2 it pings it, and gives No Network for WAN 2 and switches back to wan 1 while it still has no network.


Any idea how to solve this failover issue?

 

[Payam Nab]

So I checked almost all the threads on Asus failover/failback found by google and it seems like this is a known and not solved issue on all Asus routers both original and merlin firmwares