@BrianMal 

I'm also having the same issue with the periodic/semi random white blinking LED ring on the S515 setup as a 3 way. I have it showing in HomeKit and it the light reports itself on and off multiple times every minute even though the actual lights to load are not on and off.

My theory right now is that my other "dumb" 3-way switch in the circuit is an old backlit illuminated rocker (likely using AC to a small filament) that pulls enough watts to light the rocker switch. That maybe triggering the smart switch to think that the lights are on, and then off.

Need to get a non illuminated dumb three way to test this out further.

  @TechBro 

Since I first reported several issues to tp-link in January, I have received 4 weekly firmware updates, each one fixing a part of the issue. I received the last one this morning that fixed the switch not coming back online after a firmware upgrade. However, I am not sure if they have released any of these for general distribution as others have reported they don't see the versions I am getting. All versions have been 1.0.4 but today's is 1.0.4 Build 250214 Rel 120349. I think most, if not all, your problems should go away once they release the final version.

Brian

  @TechBro 

Forgot to mention...

From what i have figured out, the switch intelligently determines whether the light is on or off by which line draws power, hence why the other switch has to be 'dumb'. Apparently, the threshold for this is around 1/2 watt. That bulb in your other switch might cause an issue so might be worth replacing or bypassing it to test.

Brian