LS300 Hourly Reboots?

We have several LS300s. Most are running 4.4.4.004 software. Firmware is p3111301,54182. They all reboot about once per hour. All periodic reset fields are turned off (set to 0). Why are they rebooting so often? What do I need to do to stop this? I tried doing a software upgrade on one of them to 4.4.4.p05 but it doesn’t seem to have helped. Any ideas?

Followup: The keepalive IP was set to something that was non-responsive. Keepalive failures result in a reboot.