Some devices log as "failed" while still reporting to Indigo

When I use Interfaces>Z-wave>Report Failed Modules to Event Log I get a list of several sensors that are, in fact reporting to Indigo. However, in one way or another, mostly Define and Sync, they are not responding correctly.

Why would a device that is sending status to Indigo be listed as failed? Notably, these are ALL PIR motion + sensors, though not all the same brand or model.

[matt (support)]

If the Z-Wave controller tries to send a message to a module and it fails (no acknowledgment), then the controller flags it as failed which is what is returned from that list. If the module is battery operated, then trying to send any commands to it (including the commands used to Sync it) while it is asleep will result in it being flagged as failed. Point being, a battery operated sleeping module (like most motion and multi-sensors) must be awake to receive commands from Indigo. I believe the next time the module sends a out a command (ex: motion detected) the Z-Wave controller will unmark it as failed. Indigo doesn't have any control over how the Z-Wave controller marks modules as failed or not – that menu item is just dumping what the controller things is failed to the Event Log.

Thanks! Makes sense.