I'm new to Kasa but not new to electrical/electronic troubleshooting. After installing a single Kasa 3-way switch on a relatively large 4-way circuit everything worked great  when operated from the switches. However, when using the app it was a one press to turn on and two presses to turn off. The Kasa switch, after turning on the lights, would decide that the lights weren't on after about 13 seconds. Pure confusion. I double checked everything, all good. The switch was installed at the power source for the circuit. I experimented with adding more load to the circuit thinking that perhaps the sensing circuitry could not reliably sense just the 25 watts or so in the ceiling light circuit. No joy. Apparently, this is an issue that has plagued the Kasa community going back some six or seven years.

I scoured the Internet and watched hour-long videos investigating this very scenario but none led to a successful conclusion. Generally, it is believed that a second 3-way switch is not necessary. If a second 3-way switch is installed the Kasa app simply turns off the "brain" of the second 3-way switch and it becomes just an expensive 3-way switch.

I decided to add a second 3-way switch to see what I could learn. And that is where it got really interesting. So, when I added the second 3-way switch, its mate, the other 3-way switch on the same circuit was already configured as a single switch. Just as soon as I wired the 2nd switch, but not yet configured it, the app functionality using the 1st switch worked perfectly. Very interesting!

To learn more I reset both switches and configured them as a pair of 3-way switches. No joy!

I reset them both again and configured them both separately and individual, single, switches. PERFECT! The app shows the two switches separately but either one in the app operates the circuit perfectly.

As another test, I deleted the second switch, which is on the load side, from the app, and the original, power side, switch continues to work perfectly from the app.

To kee from having a switch that is blinking all the time I again configured the 2nd switch as a single and renamed it as a "secondary" switch and removed it from its assigned room, in the app, so I wouldn't have to look at it.

Bottom line is that in MY 3/4-way circuit I need the 2nd 3-way switch, and it needs to be configured as a separate switch. Combining it as is typical for 3-way switches turn off the "brain" of the 2nd switch and the circuit fails to function properly in the app. In all cases the two separate switches always work perfectly from when using their paddles. I can group my various circuits in my home theater room and they work perfectly in syncronization in every case. Case closed!

I'm new to Kasa but not new to electrical/electronic troubleshooting. After installing a single Kasa 3-way switch on a relatively large 4-way circuit everything worked great  when operated from the switches. However, when using the app it was a one press to turn on and two presses to turn off. The Kasa switch, after turning on the lights, would decide that the lights weren't on after about 13 seconds. Pure confusion. I double checked everything, all good. The switch was installed at the power source for the circuit. I experimented with adding more load to the circuit thinking that perhaps the sensing circuitry could not reliably sense just the 25 watts or so in the ceiling light circuit. No joy. Apparently, this is an issue that has plagued the Kasa community going back some six or seven years.

I scoured the Internet and watched hour-long videos investigating this very scenario but none led to a successful conclusion. Generally, it is believed that a second 3-way switch is not necessary. If a second 3-way switch is installed the Kasa app simply turns off the "brain" of the second 3-way switch and it becomes just an expensive 3-way switch.

I decided to add a second 3-way switch to see what I could learn. And that is where it got really interesting. So, when I added the second 3-way switch, its mate, the other 3-way switch on the same circuit was already configured as a single switch. Just as soon as I wired the 2nd switch, but not yet configured it, the app functionality using the 1st switch worked perfectly. Very interesting!

To learn more I reset both switches and configured them as a pair of 3-way switches. No joy!

I reset them both again and configured them both separately and individual, single, switches. PERFECT! The app shows the two switches separately but either one in the app operates the circuit perfectly.

As another test, I deleted the second switch, which is on the load side, from the app, and the original, power side, switch continues to work perfectly from the app.

To kee from having a switch that is blinking all the time I again configured the 2nd switch as a single and renamed it as a "secondary" switch and removed it from its assigned room, in the app, so I wouldn't have to look at it.

Bottom line is that in MY 3/4-way circuit I need the 2nd 3-way switch, and it needs to be configured as a separate switch. Combining it as is typical for 3-way switches turn off the "brain" of the 2nd switch and the circuit fails to function properly in the app. In all cases the two separate switches always work perfectly from when using their paddles. I can group my various circuits in my home theater room and they work perfectly in synchronization in every case. Case closed!