from what I learn about R80.10, Topology is much more enforced than before.
An example: If topology is wrong on the object, it can discard the trafic without blocking it. (database correction solve the issue)
I'll build this morning a lab with R77.30 and R80.10 with 2 ISP and try to replicate your issue.
Did you try to disable Sxl for testing purpose ?
Could you kindly provide me some more debugs.
ping 18.104.22.168 //from one host on your network
fwaccel off //(if you can)
fw ctl zdebug drop | grep 22.214.171.124
fw monitor -e "host(126.96.36.199),accept;"
fw ctl affinity -l -r -v
remove has much information about host ip etc ... we need interfaces and NAT.