Nope ^^, I know there is so much useless error displayed, but I prefer that, easier for me to repair and check for error.
So, on the version you are using, the plugin detect itself new device when it see the information in websocket.
Since 2/3 version deconz use an hidden group that group ALL your devices, but this group is hidden.
When you start the plugin, it synchronise with deconz, but it can't see this hidden group, so the plugin don't memorise it. So later, during you use, you will trigger this group, and the plugin detect it, add it in the device list, and never ask you again, up to the next restart/reboot.
For information, you can see this group in your device list too, it's called "GROUP_All"
I know, I can avoid this message, but deconz is a "moving project", this hidden group is new, and can disapear soon, so for the moment I use the lazy way and let the message.
You can have this message everytime you are adding a new device in phoscon after having loading the plugin. It just mean the plugin have find a new device and add it in the device list, nothing important if all is working, but usefull if you have bugs.