So finished installing 3-way switch. Tested it prior to setting syncing them and setting them up in Kasa and they behaved exactly as a 3-way switch should. I then connected to one, updated firmware and disconnected. Connected to the other, updated firmware and then synced back to the first switch. Installation completed as per instructions.
Now, the "Master" (that is synced to the network first) works fine. No issues here at all. The "Slave" (the switch that just syncs back to the "Master" during the installation) on the other hand doesn't work properly. I physically press the switch and it makes the "click" noise but nothing happens. I physically press the switch again and the light turns on for ~3.5 seconds then the light automatically turns off.
Anyone have any experience with this? Any idea what could be going wrong?