WiFi signal lost when Ethernet cable connection.

Please help.

I just bought last week this wonderful device, I am until now very happy , and getting to know about it.

Nevertheless ,I am finding a problem and I need some advise, please.

I need to be connected only through the Ethernet cable for a job task.

No problem about this .

But for whatever reason....WiFi signal to supply other devices (out of the job tasks) dwindles ....and until I disconnect Ethernet cable form router...there is no WiFi available.

As soon as Ethernet cable is disconnected, WiFi comes back strongly to light up tablets and mobiles.

Please, can you help???

MANY THANKS