Why these Yeelight errors?

I get always this error:

2018-08-01 23:09:24 ERROR (Thread-20) [homeassistant.components.light.yeelight] Error when calling <function YeelightLight.set_default at 0x68840ae0>: {'code': -5000, 'message': 'general error'}

Can someone explain me what is the meaning and how to solve ?