Hey guys, I noticed this problem a few days ago and I don't know hot to fix it, so I need your help...
So yeah, like the title says, my amp's volume gets quieter without changing anything, it just happens while playing. And when I turn my amp off and on again, it's just as loud as before.

I'm playing through a Roland Cube 30X with a POD X3 Live as a preamp.

could something be hitting the volume knob? Because the cubes are very digital its impossible for most people (even most guitar techs!) to just open it up, locate the problem and fix it. First thing - see if it happens without the POD. If it dosen't, then send an email to Line6. If it does still happen, then send an email to Roland.