Please aid my understanding

There are several places in southern Missouri and Northern AK that have signs in the business places and hotels that warn of inaccurate gps operation. I can say the sign is right. If you rely on gps to find the address you enter,you will be taken several miles out of your way and never end up at the address you entered.
The signal is stron, the land is flat, and I believe 5 sattlelights are in use.
I wrote to Tom Tom and they did ot speak to the problem. I am now in Osage beach mo and I had to turn off my unit. It took me three miles past my hotel , and stoped me in a empty field.

Can you explain this?