As I’m playing, the volume seems to cut down to about 75% and then it goes back up to 100% randomly. There’s also a bit of static noise and distortion sounding when this happens I just bought new power tubes to make sure that wasn’t the problem. But the problem still persists. It happens on both inputs, one and two. In addition, the preamp tubes were also replaced within the past year or so does anybody have any idea what the issue might be before I take it to a technician?