I have the same problem. It rarely seems to occur when I first power up, it becomes evident after playing for a while. I also had the "cutting out" problem described here. It took fully removing/readjusting the sled and the docking connecter wires to get a position it liked.

I plan on getting the LED and button kit when Stu at Eutronix has them ready. Perhaps he'd be willing to re-solder the docking connector wires for a fee. Hopefully he could check for the problems described here and here if necessary. Maybe the right-volume problem is related to one or more of these?