Flex and Wifi

I am having a very strange problem.  When I plug in the Flex box via HDMI to my LG Smart TV, the TVs wifi connection becomes very unstable.  By this I mean, the wifi signal drops intermittently.  At first, I thought it was the cable modem, then my wifi router and even the TV itself.  As this began shortly after installing the Flex box, I tried to disconnect the box (unplugging the HDMI cable and power).  To my surprise, and I mean surprise, the wifi signal drop stopped.  Exactly how this could occur is beyond me.  I hope someone can explain this.