LDAP Authentication

I login to the fortigate web admin using my LDAP User and here my config. Everything is working fine, i able to log on to the Firewall. But when i upgrade the firmware on primary firewall then when secondary firewall take over then i can't login using LDAP users. 

If i remove set source-ip then both firewall able to login. Anyone know why?

IP 10.202.151.1 is interface on Fortigate which connected to the LAN (Core Switch)

FW01 (AD) # show
config user ldap
edit "AD"
set server "10.203.248.31"
set source-ip "10.202.151.1"
set cnid "sAMAccountName"
set dn "dc=mydomain,dc=id"
set type regular
set username "mydomain\\admin.forti"
set password ENC xxxxxxxxxxxxx
next
end