That does sound unusual. When you say the 'relay click several times per second' is the plug itself turning on and of that quickly? You can confirm by connecting a lightbulb to the plug. The plugs will flash when loosing signal with your router, thorough they should automatically re-connect. Can you confirm the plugs are located in in area with strong wi-fi signal and try moving them closer to your router? It sounds as if the plugs themselves are not properly paired to your Wi-Fi.

  @Otrip  Yes that quickly, with no load attached, nothing plugged in. Has nothing to do with the wifi source which is within 8 feet. It starts flashing instantly as I plug the smart plug into any outlet!

  @DDatt 

The plug itself flashing quickly means it is in pairing mode.

Too strong if a wifi signal can ovetload the plug.

But if the relay in the outlet itself is turning on/off confirmed by plugging a lightbulb into the Kass then that is a big problem that the Kasa engineers need to investigate. 

  @Otrip No. It flashes several times per second (Like a machine gun), whether a light is plugged in or not, a lot faster than the pairing mode. There are 2 identical KASA smart plugs closer to the router than this one without any issues. It's as if the PCB has failed solder connection.

  @DDatt  did you ever find a solution to this ? 

  @DDatt   I have installed 30+ of these WiFI outlets and never had a problem until this one. It was previously working but stopped and I was unable to reconfigure it.  When I tried to reset it by holding the button in for several seconds, it went into this constant clicking with blue light flashing, like yours.  Now, that's all it will do.  I don't know how to change it.  It is just defective??

  @Madcrow I have only 1 out of 4 that still works. The other 3 went into the circular file (trash bin). The one that works operates a light, a stereo and my Amazon echo. The ones that died operated lights and small fans, minimal wattage. You get what you paid for I guess.

I just wanted to say that I have the same problem with one of my 2 plugs. The other one is still fine.

  @DDatt and everyone above. All 6 of mine died in this exact manner. You can definitely hear the relay switch clicking with every freaking blink. I've not found any way to reset the effing things. Since these were attached to my reptile enclosure set up I had to replace them already but like, what the eff? Ya know?