When I was really young our neighbor (druggy) demanded we move our septic tank because he claimed it was partially on his property. He was a complete jerk about it and kept at it. My dads a really laid back person, eventually even he got mad and had the property line surveyed. Turns out not only was the septic tank on our property, not his, but the corner of his house and part of his drive way was actually on our land. Dad spent the next few months asking him when he was going to move his house off our land.