I've started to experience what seems to be a technical issue with my new Mini Torii:

The right channel's volume knob is slipping (loosing grip) over the volume pot shaft (I suppose), as it has a sector where it becomes quite loose, as if it is not dragging the volume shaft along. After that sector, it starts having grip again. The end result is that the off position is no longer at 7:00, but has moved to about 5:00, and frankly I have difficulty referencing the volume position on that channel.
I would like suggestions to try to correct this by myself, before it gets worse, since shipping the unit back to mother ship is unfeasible. I may be wrong, but I suspect somehow the gripping of the volume knob over the pot shaft is not right. This, in spite of always having manipulated those knobs with the utmost care, since the gear's arrival.
I'm just hoping it is something I can fix at home, using some expert directions. I don't know how this piece is assembled, but I'm imagining some sort of male-female coupling between knob and pot shaft. Hopefully it may be a matter of taking the knob off and using some additional gripping medium between the knob's internal hole and the pot shaft, or maybe tightening some prisoner screw.
Any suggestions would be greatly appreciated. BTW, my volume knobs are the wooden (walnut) type matching the amp's chassis woodwork.