Incidentally, more than three customers have emailed me about their volume knobs being off-centered. In the worst case, the customer could not fully rotate the volume knob.
The tolerance on that hole in the chasis for this production was pretty terrible and when shipped with the knobs on, the pots tended to shift. The solution requires opening up the amp, loosening the POT nut, centering the POT and re-tightening. If you're ambitious, take the POT out and wrap some tape around the shaft to fill the gap before re-inserting and tightening.
Guys, I'm not proud of this issue but since it didn't exist at the warehouse before the units were shipped, we missed it. I'm deeply sorry and thankful for your help fixing the issue.