Yes, it's probably that. I've mentioned this ground wire before. Being a hollow body, you won't be able to poke the wire through from inside the body, so you'll either have to unsolder it, and poke it through from the bridge post hole, or get another bit of wire, fit that and put push-fit connectors on the two bits of ground wire so they are easy to connect. If you do that, then shorten the wires so there's not too much excess floating around in the body.