Have no idea about how these SWCGs are build but can you get directly to the cell and measure the voltage there? If the voltage there is up and current is still low then in my mind that would definitely point to the cell and not the electronics. With the right voltage on the cell the rest is just an electrochemical reaction. If it isn't easy to clip onto some terminal or connector somewhere, sometimes a couple needles, or the needle type multimeter probes themselves can be used to poke through the wire insulation, depending on the type of cable.
Al