Answer
The pilot should resolve the discrepancy using the authoritative source for that country or move the operation to a clearly permitted location. If the boundary cannot be confirmed, the conservative choice is not to fly from that point.
Explanation
Boundary uncertainty is exactly the kind of issue that should be handled on the ground. Launching while hoping the less restrictive tool is correct creates legal and collision risk problems. The pilot needs a defensible source before deciding that no authorization is needed.