My favorite motion sensor (maybe my favorite smart home device, period) is the Iris v2 motion sensor. Small, fast, does motion and temp, fits almost anywhere w/out being distracting. Very high WAF.
One of mine went south recently, I dropped it a couple of times. Thought it was done as over several days it refused to ever report anything other than motion active, and refused to reset not matter how many times I tried. After ignoring the reset attempt (insert battery while holding button down) it would just start blinking blue ever couple of seconds. Already joined to my hub so not like it was actually in pairing mode, just seemed confused. Opened it up and confirmed all solder points were solid.
So I removed the battery and set it aside. Today I decided I'd use it in the fridge as a temp sensor. Put in the battery w/the button pressed to try again to see if it would reset (never give up, right?) but once again it did not go through the reset process. I set it down on its face to do something else and came back a little later and noticed the device page said "Inactive." Ooooo...what's going on here, is this thing working!?. Picked up the sensor and went to active. Set it down and waited and it went to inactive. Tested multiple times now over a couple of hours and it appears to have self healed somehow.
Pretty happy...these are hard to find now so I feel like I've recovered a rare breed not often seen in the wild any more. 
Thought I should share for other Iris v2 owners...don't give up right away, your sensor may just need a rest... 
Hopefully this recuperation will be long-lived.
