I’ve had this strange loud crackling hiss coming from one of my Focals. I sent it to the only Focal certified technician in my country who decided it was the tweeter amp and replaced it. Two weeks later the noise came back with no input connected. He suggested replacing all the electronics which I did not agree to since it would cost $1000. Focal wrote to me and said it is not protected from the 4g/5g networks. The other monitor has had no such interference only the one which used to come and go. After 3 months of no problems, the noise came back this time it is constant. I even tried it in a different location and it still made noise. Any suggestions or help would be greatly appreciated.