Burden of proof is on the person making the claim, Opinions and interpretations are any ones guess. everyone has an opinion. have them get the line marked by there surveyor. Then you can decide from there.
I had one where a tree limb fell and broke a rafter, sent me a letter, i took it to insurance company .they asked if tree was dead? and its not. there is a fence there we assume is property line. Grows into the tree. no one has a survey. allegedly he went out and put up two pieces of rebar and said there's my line. He want me to cut the tree, I told him that i don't have the right to cut someones else's Maple tree, He would have to prove it was my tree and get the survey. He decided to cut his side of the tree, asked for permission to cross our land. we old him sure! if you have the tree guy to call us we would pay for our 1/2 . of course they came and left and we still have our half of the tree. Amazingly the fence has disappeared.
So I am sure it will eventually show up again. its been 3 years now.