Ground fault alarm

It's a TRC digital monitor that just plugs into an outlet. A digital display shuttles between volts and frequency and will generate a beep if it sees a problem with wire diagnostics. It wasn't a cheap unit. I use it frequently to check campground power and this is the first time I have seen an intermittent ground fault alert. It's pretty much the same alert that an ungrounded generator would produce. From what it says on the top of the unit, the fault generated is "open ground fault connection".
I guess my assumption is a bad possibly intermittent ground inside the pedastal.