00444 foneGEAR Headset one side louder than other

Question

I've had several sets of these headphones before and they've always worked great, but the last two I had purchased as spares sets both are louder on one side than the other. I've taken them apart, and the wiring appears to be okay. I've tried changing the balance from left to right through my computer volume controls with no difference at all. I can't figure out what the problem is. They are the exact same style and model number I had used previously but they're just not working properly. How can I fix this?