Since port-forwarding configuration changed, any bugs that were there are probably no longer relevant. There are new ones of course :), and #11925 looks similar. Please, use it for further updates, if still relevant.
For binding outbound connections to specific IP (comment:3), please see VBoxManage modifyvm "VM name" --natbindip1 "IP" in the manual (Binding NAT sockets to a specific interface).
