Powerline makes a buzzing noise once plugged in and flashes all LEDs every 15 seconds. While this is happening it will sometimes turn on and transmit ethernet for a second and stop transmitting again. 

The problem occurred two days ago, but the buzzing was for about 4 months now. It usually buzzed for a minute and worked fine afterwards.

I read other threads and havent yet found an answer. I measured decibels of the buzzing via two apps and it showed below 40. I have tried resetting, but the powerline seems to ignore it completely, because LEDs dont go off and WiFi LED doesnt flash. I tried to pair the two, but it doesnt respond in any way and keeps doing what it did. I tried plugging it into a different spot, plugging both devices into one room and different rooms. 

I would really appreciate it if you helped me to solve this problem.

The other one, which is with the router, is working fine.