fortiwifi 60d

hi.

it's like half an year that i have this problem. i'm trying with Fortinet support but there is no luck.

after 5-10 min using wifi. it's dead.

there is no ping to the firewall.

PING 192.168.100.254 (192.168.100.254): 56 data bytes Request timeout for icmp_seq 0 Request timeout for icmp_seq 1 Request timeout for icmp_seq 2 Request timeout for icmp_seq 3

i try a lot of things. but nothing helps. 

i'm using the last version of FortiOs 5.4