I just got a new Keyboard a few days ago. When using headphones and not playing, I get a dull crackling EMI noise in the left ear. It sounds like something in the unit is doing something at some interval, and it’s bleeding into the left channel. It’s not audible when playing, but if you rest for a moment, you can hear the noise if it’s happening at that time.
My concern is that there is a hardware fault. I am on the latest firmware, have a switched outlet, and do not have a USB plugged in when this occurs. The headphones being used work without issue on other synths.