That's a weird one, and I don't know if I can be of much help since this really does "feel" like there's a networking issue here, and that's not my particular strong suit. Did you make sure that the DHCP server is off in the ECS (System --> Harware --> DHCP Server)? I know you said there are 130 phones, so I'm not sure how possible it is, but have you tried to statically set them? Maybe just set a test group of phones with static address and network info. See if they stay up while the others reset.