Well its really a case of when JVC originally diagnosed what was responsible for the problem the said diagnosis involved an internal inspection of the device, so remote faultfinding on some "uncommon" problem isn't really a very easy task as one has to be armed with suitable equipment, but the original faultfinding statement of the fault being caused by "cold solder" is liable to indicate that a dry joint was found on the PCB track, with experience suggesting that this could possibly be around the charging regulator circuitry. There isn't really any option but to bring the subject up with JVC's technical department, and stating exactly what you have posted. A decent repair depot could no doubt find the reason for the fault, but its much better to contact JVC first.