C++ Weird Issues with Dynamic cast - Polyrmophism (Changed bool) - vector

Question

I am trying to dynamic_cast an instance from a vector by
AWorld.Unit_IndexB = AWorld.topof_CityIndex + 20;
for (auto i = AWorld.topof_CityIndex; i < AWorld.Unit_IndexB - 1; i++)
{
// unit found
//cout << "hit" << endl;
//int b = i - AWorld.EntitiesVector.size();
EntityUnit a;
a = dynamic_cast<EntityUnit*>(AWorld.EntitiesVector[i]);
a.unit_alive;
if (a.unit_alive == false)
{
The issue is that my vector - all the EntityUnits are pushed on with a value of unit_alive = false;
Yet when I dynamic cast for some reason it always returns the unit_alive as true, note that it appears all other values are correctly cast EXCEPT BOOLEANS which all turn out false.
I know you should avoid using dynamic cast but I cant think of any other way to do it in this situation, since I need to replace an element in a vector with a new one of subclass type.
I'm doing this at the end
AWorld.EntitiesVector.erase(AWorld.EntitiesVector.begin() + i);
AWorld.EntitiesVector.emplace(AWorld.EntitiesVector.begin() + i, new EntityUnit(a));
// AWORLD
class World
{
private:
World(const World&);
void operator=(const World&);
public:
const int pointsInLine = 70; // how many points in a line
const int lines = 180; // lines must be multiple of 30
// this is the grid size, 180 x 70, the grid is connected top to bottom and left to right, so 0x - 1x = 180x and 70y + 1y = 0
std::vector<void*> path;
vector< CWaypoint*> PathToBeMade;
vector<vector< CWaypoint*>> HiFiWaypoints;
vector<vector< CWaypoint*>> LoFiWaypoints;
vector<CWaypoint*>JumpPoints;
vector<vector< CWaypoint*>> AIRCRAFTWaypoints;
vector<vector< CWaypoint*>> NukeWaypoints;
vector <CEntity*>EntitiesVector;
vector <EntityCity*>CitiesVector;
vector <EntityUnit*>UnitsVector;
int topof_CityIndex; // beginning of city index is always 0
int topof_UnitIndex; // beginning of unit index is top of city index + 1
int Unit_IndexB; // Where blu's unit index begins
int Unit_IndexG; // where greens unit index begins
int Unit_IndexY; // Where yellow's unit index begins
int index_current_entities;
bool showConsidered; // used in pathfinding
bool AllowPoles; // This bool controls whether the pathfinder will allow something to head
// north or south of the poles, bear in mind, this is for nukes & aircraft only
bool gamestarted = false;
int source_x, source_y;
int target_x, target_y;
int northpoley; // maximum point north - excluding nukes
int southpoley; // maxmimum point south - excluding nukes
const int max_units = 100;
tle::IModel* P;
string unitdefs[15];