The TRC web site is pretty short on details. There is one mention of testing for "open ground" so I'll assume that's the type of ground fault it's reporting. It's not possible for the tester to directly test for an open ground, so some other thing or things are monitored and interpreted, and one of those interpretations is open ground, and it's usually correct but could be wrong. For instance, the tester could interpret a few volts difference between the ground and neutral wires as an open ground. But if there's a long wire run from the point where the neutral is actually grounded, there could legitimately be a few volts difference. The varying load presented by your rig and other rigs could send the neutral voltage back and forth over the threshold where a fault is declared. After saying all that, the short version is that maybe there's a real problem with the ground wire, and maybe there isn't. It would take probing with a meter to make a better diagnosis.
2009 Fleetwood Icon 24A
Honda Fit dinghy with US Gear brake system
LinkPro battery monitor - EU2000i generator