Same with mine. When he was new to us, he ran away twice so I put him on a leash strictly and put a GPS tracker on him. Thought he just wasn't one of those off the leash dogs. A year later a friend of mine told me "just cut him loose". I told him he runs, he looked at the dog and said "nah. He isn't going to. Try it."
Was hectars and hectars of his private forest, so I thought "what the hell, we'll find him with the tracker when he's hungry" and massive surprise: He really never ran off. Not that day and never since. 20m ahead, 20m back, never have to worry, as soon as people can be heard or he loses sight of me he's by my side immediately.