@AMDPower

It's true that each electronic and/or smart switch needs to have constant power and that the KS230 can't be used with 4-way switches.  That's why it's sold as a "kit".  However, a better hardware implementation would have allowed for multiple smart, remote, and 4-way switches in the same circuit.  4-way switches don't cut off power.  They simply toggle the line between four different paths but they always allow line voltage through to the next switch.  Lutron's Maestro series has been able to work in a 4-way cicuit for many years and even allows for a mixture of switches in the same circuit.  Unfortunately, they're relatively expensive electronic switches and they aren't "smart" in the sense that they can be network connected.  I expected much better hardware from TP-Link that would have worked like the Lutron, but included Wi-Fi too.

@Connu Agree.  I have a lot of MyLeviton devices.  Same thing.  And their remote switches actually work with their wifi line AND z-wave line.  The main switch does all the work and the others just signal the main switch.  Cheapest implementation is through the traveler but WiFi is pretty inexpensive these days and could have been done that way as well.  I actually set up two regular Kasa dimmers to work this way as a test using my Hubitat.  It "works" but unfortunately with the Kasa protocol being UDP, you need constant polling for it to work which causes a delay.  Further, physical pushes on the main switch don't send OUT any UDP messages.  Again, needing constant polling.  

@Connu Mine are not mounted side by side, but do not appear to be that drastically different.

Thanks @Garage223.

Mine is bright enough that you would notice it across the room.  I'm really thinking I got a defective unit.  I ordered another kit and should have it today.  We'll see.

On a different note, I noticed that Amazon released a series of smart switches under it's "Basic" brand.  The four new switches include a 3-way dimmer and also need a neutral wire like the KS230 kit.  It's a good-looking unobtrusive switch that offers support for routines and schedules, but only works with Alexa.  Like the Kasa KS230, Amazon says it doesn't support 4-way circuits.  However, they don't require a second smart dimmer switch or a special remote switch in a 3-way circuit.  This leads me to believe that it should actually be able to work in a 4-way circuit as long as you can get the line and load to the main switch.  At only $21.99 retail, it’s significantly less than other switches.  Curiosity is killing me, so I've ordered one to play with on my 4-way circuits.  TP-Link, can you finish polishing up the firmware by taking care of the last few issues and maybe lower your price a few bucks to boot?

Amazon Basics 3-Way Smart Dimmer Switch, Works with Alexa, Neutral Wire Required - A Certified for Humans Device - - Amazon.com

Hi @Carl,

Good to hear from you!  I thought you might have quit.    It's disapointing that they had to disable features and force the remote nightlight to always be on in order to get the kit to mostly work.  Now the nightlight is neither a nightlight (since it's always on, even during the day) nor a power indicator (since it's always on regardless of whether the lights are).  On top of that, my indicator light is many times brighter than my other Kasa switches.  I've got a new kit on the way and will keep you posted on whether this is an issue or simply a bad switch I received.