Latest steps:
I Removed the device, Performed factory reset on device, re-linked the device. Status: Failed. Heartbeat still missing.
I Upgraded ISY99 firmware, then again removed the device, performed factory reset on device, and re-linked the device. Status: Failed. Heartbeat still missing.
Upgraded firmware details:
Any other ideas? This doesn't appear to be local to any particular device. though I will say that motion sensors do show the heartbeat/low Battery like the other devices used too.