Routing with 2 wan and ipsec: can't ping wan1

[Arthur]

i have a network like this

lan
            |
            |
    "vpn / firewall"
            |
            |  wan1
    |_
    |                |
  wan1          wan2
    |___________|
            |
        pfsense

i have bind a VPN ipsec with pfsense wan2 and the "VPN/FIREWALL". All is ok
When from the lan i ping the pfsense wan2 is ok.
But when from the lan i ping the wan1 is KO !
I think that is a mistake/bug in the routing of pfsense !??
When i ping Pfsense wan1,  Pfsense try to answer  with use the wan2 interface.
So my computer refuse the answer because the answer come from the wan2 ip and not from the wan1 ip !
When i ping the wan1 pfsense must answer with use the wan1 ip !
I think that is because pfsense create an auto static route that tell to use wan 2 (that is the vpn interface) to talk to  "vpn / firewall" ip.

any solution to resolv this ?
thanks to any idea