troubleshoot PFE Invalide interface

Dear all,

How can I troubleshoot a PFE Discard "Invalid interface" ?

show pfe statistics traffic    
Packet Forwarding Engine traffic statistics:
    Input  packets:                 1758                    1 pps
    Output packets:                 1490                    0 pps
Packet Forwarding Engine local traffic statistics:                  
    Local packets input                 :                  464
    Local packets output                :                  362   
    Software input control plane drops  :                    0
    Software input high drops           :                    0
    Software input medium drops         :                    0
    Software input low drops            :                    0
    Software output drops               :                    0
    Hardware input drops                :                    0
Packet Forwarding Engine local protocol statistics:
    HDLC keepalives            :                    0
    ATM OAM                    :                    0
    Frame Relay LMI            :                    0
    PPP LCP/NCP                :                    0
    OSPF hello                 :                   54   
    OSPF3 hello                :                    0
    RSVP hello                 :                    0
    LDP hello                  :                    0
    BFD                        :                    0
    IS-IS IIH                  :                    0
    LACP                       :                    0
    ARP                        :                    5
    ETHER OAM                  :                    0
    Unknown                    :                    0
Packet Forwarding Engine hardware discard statistics:
    Timeout                    :                    0
    Truncated key              :                    0   
    Bits to test               :                    0        
    Data error                 :                    0
    Stack underflow            :                    0
    Stack overflow             :                    0
    Normal discard             :                   15
    Extended discard           :                    1
    Invalid interface          :                  270
    Info cell drops            :                    0
    Fabric drops               :                    0
Packet Forwarding Engine Input IPv4 Header Checksum Error and Output MTU Error statistics:
    Input Checksum             :                    0
    Output MTU                 :                    0

Platform QFX10002 (hardware), Junos 15.1X53-D63.9

Thanks !

Salah