Acccess internal Server from two WAN Adresses

Hi,

i have two WAN Interfaces in one Firewall Zone WAN.
WAN A has Metric 0 in Default GW and is used for all trafic.
WAN B has Matric 10 in Default GW and is only for Backup.
There is a portforwarding form Zone WAN to a server in the LAN.
Access from WAN A to the Server works fine.
Access from WAN B to the Server isnt working. I think because the response pakets are sent to WAN A since the default Route is set like this. (asymetric routing?)

How can i use WAN B for accessing my Server too?

BR

mode

was able to resolve it by installing mwan3.