PA3x volume feedback

[KeysFla]

I am running left for keyboard out to one channel. Output 1 for mic.
Sometimes I get a loud howling noise like the volume of the mic is full on. I move the two volume sliders down, then up to where it was and it plays normal.
I am thinking of opening it up and looking for bad solder joints. Loose connections. Could it be the mic input section?
Anyone experience this?

[Reuben]

Maybe try setting all your faders to around 1/2 volume when it’s off. It could be there is one assigned to mic volume that if you bump it then it jumps to that position. I think most sliders only become activated if moved and then it will jump/catch it.