download haven't traffic info via mirror port

Hi All

I use FortiGate 301E mangement FortiSwitch 448D.

Download haven't traffic info when I mirror FortiGate 301E connect core Switch port on core switch,

but Download have traffic info when I mirror core Switch connect edge Switch port on edge switch. Core switch and edge Switch both FortiSwitch 448D.

FortiGate and FortiSwitch both v6.0.4

config mirror    edit "L7"        set status active        set switching-packet enable        set dst "port22"        set src-ingress "port1" "port2"        set src-egress "port1" "port2"    next end