I've used the Z-Wave Poller app for some time now with a few GoControl plug in Z-Wave dimmers and recently noticed that one of them had stopped responding to polls. Turning error logging on for the poller app showed (something similar to) " Poll: Failed Floor Lamp --> 300" (sometimes '60' appeared instead of '300') whereas the dimmers that were properly responding to polls showed "Poll: xxxx --> 10". More ominously, the state variable on the device page for this dimmer showed "failed: true" and the 'polled' state variable no longer showed 0 like the others but showed a nonzero value. Yet the dimmer seemed otherwise functional, turning on and off and diming as expected; just the on/off status was not updating on the device details page or usable by apps.
After several days of this (I have an alert that checks for lights inadvertently left on that kept crying wolf) I had resigned myself to resetting it to see if the problem went away, or swapping it out if need be. As this particular lamp was used in 21 apps & rules, the Z-Wave habit of assigning a new device number on every inclusion made this an obnoxious task. If this were Zigbee, a quick device reset and rejoin would tell me everything I needed to know (to be fair, if HE supported 'Z-Wave replace' it would have been equally simple to do a reset, and much easier should the device require swapping out). And the device itself was located behind a large sofa that difficult to access. So it wound up as another item on my to do list.
Anyway, this morning a momentary utility power blip cycled power to everything in my house not on a UPS. And lo and behold, the problematic Z-Wave dimmer began responding normally to polls, its state variable once again showing 'failed: false' and 'polled: 0' like the other normally operating dimmers. It had slipped my mind that something similar happens with one of my GE 14291 switches once in a while. Pulling/resetting its 'disable' tab fixes it as well. Apparently the MCU's in these things can benefit from a reboot now and then, though its odd how the polling functionality was the only feature to be impaired.