Adding firewall to Device Rule failed

Adding firewall to Device Rule failed

hi dear 
i have 2 firewall, fortigate version 6.4.2 and 6.2.3, 
i added my 6.4.2 device to device rule successfully but when i trying to add 6.2.3 device a get this error.
both device pass validation procedure.  
how should i solve this problem ?


config system console8278: unknown action 3\ncommand fail. return code -1\n 
set output standard Not Executed
end Not Executed
show full-configuration Not Executed
config system console Not Executed
set output more Not Executed
end Not Executed
Problem while fetching configuration from device :::2