I also had an issue that resulted in TP-Link discovering a bug. Yes, the developers are in China. I also use Load Balancing, but not in failover mode. Good luck!

According to Roberto's list, it is!

To me, it seems that the TL-R470T+ supports only UDP and TCP forwarding. I'm not sure but maybe you'd need GRE (which is an entirely different protocol) being routed.. please ask the support in your...

The "combination Modem / Router" needs only one cable. I would configure that modem as "Bridge mode". It might still have a private IP like 192.168.0.1 but that will get irrelevant if you're using...

I don't see bugs in your config (assuming you're using "Advanced -> NAT -> Virtual server". Some have reported that they needed to restart their routers. I also have portforwarding enabled but I use...

I might be wrong but isn't "Policy Routing" in "Advanced -> Load Balance -> Policy Routing" made for this case?