SNAT traffic between Ingress interfaces

I think the answer is about SNAT automap self-IP ie which self-IP it will use. For resilience it will always prefer to use a floating IP address. You can see this here: https://support.f5.com/kb/en-us/solutions/public/7000/300/sol7336.html?sr=58481983

Add a floating self-IP ( ie in traffic-group-1 ) to the egress VLAN and you shoudl find that it uses that instead.