Risk of damage to neighbor's curbstones

If the neighbor unlawfully builds over the boundary, tolerance can only become customary law after one hundred years! However, I gladly recommend another thread from the recent past, which also dealt with a boundary reinforcement: – in this context, one should be warned not to equate the boundary line according to one's own belief (or even according to the position of the boundary stones) with the legally determined boundary line: how certain is the finding that only the stones lie on his property, and their foundation already on the property of the original poster(s)? Is the bastard at least the husband of the shrew and thus punished through informal channels, or do you have TWO such neighbors to deal with?

Does the neighbor really have to tolerate even a temporary dismantling of his property? Let's say he just happens to show up with potential buyers and the path is currently blocked? Doing this without any prior notice can really backfire...

That should be proven first, shouldn't it?

Another major problem is that the house is currently empty because it is to be sold. Contact details of the owners are not available. So we cannot just seek a conversation.