First of all i would like to explain why i like to address this as a bug.
From a player point of view, the map is fully revealed but you have not achieved 100% map clear. for any player that does not understand how fog of war actually works, it is considered as a bug.
Is it possible to increase the fog of war in minimap or show more feedback on the minimap to say which is the part of the map you have not discovered? because i normally get to a 97% map clear, just to realise i haven completed the map, BUT the map is already fully revealed, so i have to rewalk the map 2~3 times to find the invisible black spot. It really kills the game experience so please work on that thanks =)
Solutions: change tint of fog of war to red when near completion so as to
A: Encourage player to clear the map
B: Prevent players like me to be suffering this 100% map achiever problem.

