@Wizard_of_Uz 

I would restart the entire Deco system, see if that still happens.

Test the remote and local connection meaning have your phone on Wi-Fi or cell to see if it happens in both instances.

Mainly to see if you can control the switches remotely on Kasa. If you are not able to, select one of the switches and go into the device settings. If remote control is disabled there should be a ticker where you can enable. If remote is working, then you will not see it.

@Tony

First of all, thank you for the ideas!

The only thing I had already tried was rebooting the entire Deco system. That didn't work. I tried again now, just in case, but I still get the same error.

I then tried the other idea you suggested. I turned off Wi-Fi and went through 5G on my phone. I tried to toggle the switches via the Kasa app and the switches all worked correctly. I then tried toggling the switches via the Deco app, but encountered the same error.

It's strange because the Deco app does "see" and list all of my switches and the switches and the mesh system are both manufactured by TP-Link, so this should all theoretically be a seamless integration.

I guess I'll just wait until a firmware update comes along and hope that things change for the better.

Thank you, once again, for trying to help me out. Much appreciated!