DW and I drove from NYC to near Wilmington, NC last month. We went via the DelMarVa Peninsula and even thereafter stayed off the major highways.

According to the GPS, I drove through a lot of cornfields. It was pretty clear it either did not know where we were or did not know where the road was on numerous occasions, and I suspect the later in most cases.

It's a tool. Only a tool. It needs to be checked against other tools, if you really have no clue as to wehre you are. other tools would include maps and your own common sense.