What is Yeelight error 5006...?

I’m getting these error message all the time in “Developer Tools → Info”

Error when calling <function YeelightGenericLight.set_default at 0x7.....>: {'code': -5006, 'message': 'illegal request'}

Unable to update device 10.0...., Sofa Lamp: A socket error occurred when sending the command.

Unable to update device 10.0...., Sofa Lamp: Bulb closed the connection.

Any ideas what causes error -5006?