Cisco IP Phone 7960 kill the Asterisk server

Hey Everyone.

I am having an Asterisk with the latest firmware and I am having 30 SIP phone Cisco 7960. But when a phone is being unplugged from the power source and the Ethernet cable stay on the phone, somehow that phone start killing the Asterisk server. I start to lose more and more phones randomly and the server start to timeout my request I barely log in there. I start inspecting the phones in the building manually and I always find some that is unplugged from the power source but connected to the switch. I have a Pfsense TFTP server that provide the configuration for the SIP phones, not the FreePBX/asterisk itself(if that make any difference)

Brief update:

I have found out that this event is something CISCO have caution for this event :
" Always unplug the upstream Ethernet cable from the phone before unplugging the power supply. Unplugging the power supply before unplugging the upstream Ethernet cable could result in a service interruption on the network. "
source - … 0trbS.html

So what I read in other cisco articles is that if the phone is unplugged while the Ethernet is running, the phone start draining power from the switch and that lead to network interrupts.
Now we decide to give it a try with PoE and this should solve our problem.
I will keep on update.