I have the above speaker system on my computer and noticed music sounding off recently and figured out some sound comes out the right speaker but not everything. Specifically there is a few songs where the sound does not come out of the right speaker at all. I unplugged the speakers themselves form then subwoofer and plugged them into an iPad and tried the songs and they work just fine so I assume it has something to do when plugged into the subwoofer but not sure what it could be.
Try plugging the speakers into the PC without the subwoofer. See if that helps at all. I had the same issues but with different speakers and it was the left that was quite, the only solution I found was to use a system restore point to October as it is a win10 bug.