I have a rarely used ZED14 and in the last concert it was playing up.
There is an echo and crackle that comes from channel one when the fader is moved. The sound is heard regardless of whether the channel is mute or not. It also happens regardless whether there is a signal entering the channel or not. It also can not detect any signal coming from the jack insert. I have not tried the XLR mic input.
Also if I do not touch channel1 fader but leave it at about 0db, and then move the master fader up and down, it makes the same crackle and echo but at a much lower volume. It sounds more like scratching vinyl.
And on the channel1 control, the PK! lights up bright at about -5db.
My sound engineer said that during the event there were a few other channels making the same noise but right now in my workshop it seems to be only channel1.
Shall I open up the mixer and look at the fader? Perhaps clean it.