I would think that the read-out of a recording meter is very unreliable as to assessing channel balance. First, the needle is bouncing around. Second, you have no way of knowing how the material was encoded into stereo, meaning the fault may be in the recording. Further, what do you know about the state of calibration of your meters? IMO, if you don't hear the problem, why drive yourself nuts over a few dancing meter needles? Try feeding each meter separately with a single signal; you don't even have to know for sure the voltage or db, so long as it is the same signal fed alternately to each channel. This way you might determine if the meters are equally sensitive.
If the cartridge is fairly new, you could make a case with the dealer to replace it, if all else fails. A decent cartridge should have inherent channel balance within less than 2db, but I don't know what bible that is written into.
By the way, as to your response to my earlier diatribe, getting the azimuth "right" is not going to cure your channel imbalance, if indeed there is one. That was sort of my point.
