Before test, I configured DHCP and set lease time to 1h.
Rechecked FW 3.0.9, DHCP REQUEST flood occurs exactly after 30 min, first re-lease timing.
In FW 3.0.10, after 30 min, only 1 pair of DHCP REQUEST- DHCP ACK is logged... works as expected!
As far as I watched 3 times re-lease process loop, looks stable.
Thanks @emil, finally my flic buttons back to network!
Hope this FW solve @yea's and @Djelibeybi's problem too.