Asterisk restart after resetting multiple phones

I have 25 Aastra 6753i phones connected to my system (Xeon E3 1230 V2, 16GB ram, 256GB SSD) -
Distro:
PBX Firmware: 6.12.65-30
PBX Service Pack: 1.0.0.0
Asterisk Ver. 11.19.0

When all phones reset at the same time and they all try to Get their config. files (HTTP) Asterisk will continue to run for about 5 minutes and reset. During this time the Freepbx GUI does not respond.

Has anyone else seen this or maybe could point me in the direction of what to look for?

Thanks.