Thanks to Master Kyp i chanced the way i set the Default HUD class in the gamemode constructor from:
static ConstructorHelpers::FObjectFinder<UBlueprint> HUD(TEXT("Blueprint'/Game/Blueprints/HUDBlueprints/MainHud.MainHud'"));
if (HUD.Object != NULL)
{
HUDClass = (UClass*)HUD.Object->GeneratedClass;
}
Too:
ConstructorHelpers::FClassFinder<AHUD> HUDBP(TEXT("/Game/Blueprints/HUDBlueprints/MainHud"));
HUDClass = HUDBP.Class;
And now it works as intended.