eWeLink Devices disappear from Homebridge randomly and after restart the homebridge service
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### What issue do you have? Please be as thorough and explicit as possible.
eWeLink Devices disappear from Homebridge randomly and after restart the homebridge service. 
Is there an option, to keep the devices persitent permanently?


### Details of your setup.
* Do you use Homebridge (with config-ui?) or HOOBS? 
Homebridge with config UI


* Which version of Homebridge/HOOBS do you have?
1.1.6


* Which version of this plugin (homebridge-ewelink) do you have? Has the issue started since upgrading from a previous version?
3.15.0


* Which eWeLink devices do you have that are causing issues? Please include product models if applicable.
Sonoff Basic, TH16, B1, RF


* Do you use your main eWeLink credentials or do you use a secondary eWeLink account for Homebridge?
I use a secon eWeLink Account with shared devices from my main account.


### Please paste any relevant logs below.
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