Are the two battery banks really separate from one another or are they just called two banks but really wired in parallel? Same question for the two inverter/chargers. On my CC the diagrams and user manual talk of them as two banks because there are two wires coming off the B+ post on the alternator. They both go to the same lead acid bank. One goes to battery B+ on #1 and the other to battery B+ on #6 – or they did before I migrated to LiFePO4 as described over the last two years in Bus Conversion magazine. The final two parts of this series of articles will appear in the next couple of issues of the magazine.
If your bus is wired like mine was with two wires coming off the alternator, you may find one has more corrosion in the terminal ends than the other. That will cause more resistance and hence less charge amps going along that leg to the batteries.
Also, look at all the battery minus chassis grounds. One of those may have more corrosion/resistance than the other. Finally, swap the monitor lines going into your panel displays to see if you get the same differential in readings off of both panels. Easiest to do by just moving the monitor lines at the inverter/chargers themselves.
Jerry