Double check all aspects of your cartridge's alignment in the headshell (front-to-rear; yaw and tilt if adjustable) and tone arm adjustment, including anti-skating and pivot height. Also keep in mind that sometimes the indicators on knobs (such as anti-skating) are not as precise as you might think. Try increasing/decreasing the setting a bit and see if that changes things.
It could be nothing more than a mis-adjustment; it doesn't have to be off much to have that degree of channel imbalance.
It could be nothing more than a mis-adjustment; it doesn't have to be off much to have that degree of channel imbalance.