Have you ever used the find my friend app?

My partner is right next to me, but his GPS says he is one mile away. I saw it change addresses from being far away, then next door, then right next to me, then being far away. I’m confused. I asked him if he had a security device installed -anti tracking/ he said no. He wondered if he is being tracked? Or followed by someone, but it came back to home. I just checked it and it’s back to the 1 mile away. It also moved elsewhere. Kinda creepy that my phone does not do that but his does. Anyone know how or why this might happen.