One last culprit...

src/server/game/Scripting/MapScripts.cpp

@@ -575,7 +575,7 @@ void Map::ScriptsProcess()
 
                 // quest id and flags checked at script loading
                 if ((worldObject->GetTypeId() != TYPEID_UNIT || ((Unit*)worldObject)->isAlive()) &&
-                    (step.script->QuestExplored.Distance == 0 || worldObject->IsWithinDistInMap(target, float(step.script->QuestExplored.Distance))))
+                    (step.script->QuestExplored.Distance == 0 || worldObject->IsWithinDistInMap(pTarget, float(step.script->QuestExplored.Distance))))
                     pTarget->AreaExploredOrEventHappens(step.script->QuestExplored.QuestID);
                 else
                     pTarget->FailQuest(step.script->QuestExplored.QuestID);