We're having the same thing happen, very intermittently on SMT-i3105 sets at one customer. OS7400 V4.70

They have 100+ phones, it happens on about 1 phone every couple months or so. We've found the phones always seem to try to DHCP bind to the same IP address, even on a power cycle, so if the address the phone wants is grabbed by something else or some other change happens in the LAN environment, the phone doesn't come up. Re-running the Easy Install seems to force it to refresh the network settings. Have never had to do the factory reset.

Most of our other SMT sites we define the phones with static IPs and we haven't had the issue. Just can't do that with this site.