Src/exchange.cpp
This is what i had in bool CExchange::CheckSpace()

bool CExchange::CheckSpace()
{
	static CGrid s_grid1(5, INVENTORY_MAX_NUM/5 / 4);
	static CGrid s_grid2(5, INVENTORY_MAX_NUM/5 / 4);
	static CGrid s_grid3(5, INVENTORY_MAX_NUM/5 / 4);
	static CGrid s_grid4(5, INVENTORY_MAX_NUM/5 / 4);

	s_grid1.Clear();
	s_grid2.Clear();
	s_grid3.Clear();
	s_grid4.Clear();

	LPCHARACTER	victim = GetCompany()->GetOwner();
	LPITEM item;

	int i;

	for (i = 0; i < INVENTORY_MAX_NUM / 2; ++i)
	{
		if (!(item = victim->GetInventoryItem(i)))
			continue;

		s_grid1.Put(i, 1, item->GetSize());
	}
	for (i = INVENTORY_MAX_NUM / 2; i < INVENTORY_MAX_NUM; ++i)
	{
		if (!(item = victim->GetInventoryItem(i)))
			continue;

		s_grid2.Put(i - INVENTORY_MAX_NUM / 2, 1, item->GetSize());
	}

	static std::vector <WORD> s_vDSGrid(DRAGON_SOUL_INVENTORY_MAX_NUM);

	bool bDSInitialized = false;

	for (i = 0; i < EXCHANGE_ITEM_MAX_NUM; ++i)
	{
		if (!(item = m_apItems[i]))
			continue;

		#ifdef NEW_ADD_INVENTORY
		int envanterblack;
		if (item->IsDragonSoul())
			envanterblack = victim->GetEmptyDragonSoulInventory(item);
		else
			envanterblack = victim->GetEmptyInventory(item->GetSize());

		if (envanterblack < 0)
		{
			return false;
		}
		#endif

		if (item->IsDragonSoul())
		{
			if (!victim->DragonSoul_IsQualified())
			{
				return false;
			}

			if (!bDSInitialized)
			{
				bDSInitialized = true;
				victim->CopyDragonSoulItemGrid(s_vDSGrid);
			}

			bool bExistEmptySpace = false;
			WORD wBasePos = DSManager::instance().GetBasePosition(item);
			if (wBasePos >= DRAGON_SOUL_INVENTORY_MAX_NUM)
				return false;

			for (int i = 0; i < DRAGON_SOUL_BOX_SIZE; i++)
			{
				WORD wPos = wBasePos + i;
				if (0 == s_vDSGrid[wBasePos])
				{
					bool bEmpty = true;
					for (int j = 1; j < item->GetSize(); j++)
					{
						if (s_vDSGrid[wPos + j * DRAGON_SOUL_BOX_COLUMN_NUM])
						{
							bEmpty = false;
							break;
						}
					}
					if (bEmpty)
					{
						for (int j = 0; j < item->GetSize(); j++)
						{
							s_vDSGrid[wPos + j * DRAGON_SOUL_BOX_COLUMN_NUM] =  wPos + 1;
						}
						bExistEmptySpace = true;
						break;
					}
				}
				if (bExistEmptySpace)
					break;
			}
			if (!bExistEmptySpace)
				return false;
		}
		else
		{
			int iPos = s_grid1.FindBlank(1, item->GetSize());

			if (iPos >= 0)
			{
				s_grid1.Put(iPos, 1, item->GetSize());
			}
			else
			{
				iPos = s_grid2.FindBlank(1, item->GetSize());

				if (iPos >= 0)
				{
					s_grid2.Put(iPos, 1, item->GetSize());
				}
				else
				{
					return false;
				}
			}
		}
	}

	return true;
}


Changed it to this :

bool CExchange::CheckSpace()
{
	static CGrid s_grid1(5, INVENTORY_MAX_NUM/5 / 4);
	static CGrid s_grid2(5, INVENTORY_MAX_NUM/5 / 4);
	static CGrid s_grid3(5, INVENTORY_MAX_NUM/5 / 4);
	static CGrid s_grid4(5, INVENTORY_MAX_NUM/5 / 4);

	s_grid1.Clear();
	s_grid2.Clear();
	s_grid3.Clear();
	s_grid4.Clear();

	LPCHARACTER	victim = GetCompany()->GetOwner();
	LPITEM item;

	int i;

	for (i = 0; i < INVENTORY_MAX_NUM / 4; ++i) // slot 1
	{
		if (!(item = victim->GetInventoryItem(i)))
			continue;

		s_grid1.Put(i, 1, item->GetSize());
	}
	for (i = INVENTORY_MAX_NUM / 4; i < (INVENTORY_MAX_NUM / 4) * 2; ++i) // slot 2
	{
		if (!(item = victim->GetInventoryItem(i)))
			continue;

		s_grid2.Put(i - INVENTORY_MAX_NUM / 4, 1, item->GetSize());
	}
	for (i = (INVENTORY_MAX_NUM / 4) * 2; i < (INVENTORY_MAX_NUM / 4) * 3; ++i) // slot 3
	{
		if (!(item = victim->GetInventoryItem(i)))
			continue;

		s_grid3.Put(i - (INVENTORY_MAX_NUM / 4) * 2, 1, item->GetSize());
	}
	for (i = (INVENTORY_MAX_NUM / 4) * 3; i < (INVENTORY_MAX_NUM / 4) * 4; ++i) // slot 4
	{
		if (!(item = victim->GetInventoryItem(i)))
			continue;

		s_grid4.Put(i - (INVENTORY_MAX_NUM / 4) * 3, 1, item->GetSize());
	}

	static std::vector <WORD> s_vDSGrid(DRAGON_SOUL_INVENTORY_MAX_NUM);

	bool bDSInitialized = false;

	for (i = 0; i < EXCHANGE_ITEM_MAX_NUM; ++i)
	{
		if (!(item = m_apItems[i]))
			continue;

		#ifdef NEW_ADD_INVENTORY
		int envanterblack;
		if (item->IsDragonSoul())
			envanterblack = victim->GetEmptyDragonSoulInventory(item);
		else
			envanterblack = victim->GetEmptyInventory(item->GetSize());

		if (envanterblack < 0)
			return false;
		#endif

		if (item->IsDragonSoul())
		{
			if (!victim->DragonSoul_IsQualified())
			{
				return false;
			}

			if (!bDSInitialized)
			{
				bDSInitialized = true;
				victim->CopyDragonSoulItemGrid(s_vDSGrid);
			}

			bool bExistEmptySpace = false;
			WORD wBasePos = DSManager::instance().GetBasePosition(item);
			if (wBasePos >= DRAGON_SOUL_INVENTORY_MAX_NUM)
				return false;

			for (int i = 0; i < DRAGON_SOUL_BOX_SIZE; i++)
			{
				WORD wPos = wBasePos + i;
				if (0 == s_vDSGrid[wBasePos])
				{
					bool bEmpty = true;
					for (int j = 1; j < item->GetSize(); j++)
					{
						if (s_vDSGrid[wPos + j * DRAGON_SOUL_BOX_COLUMN_NUM])
						{
							bEmpty = false;
							break;
						}
					}
					if (bEmpty)
					{
						for (int j = 0; j < item->GetSize(); j++)
						{
							s_vDSGrid[wPos + j * DRAGON_SOUL_BOX_COLUMN_NUM] = wPos + 1;
						}
						bExistEmptySpace = true;
						break;
					}
				}
				if (bExistEmptySpace)
					break;
			}
			if (!bExistEmptySpace)
				return false;
		}
		else
		{
			int iPos = s_grid1.FindBlank(1, item->GetSize());

			if (iPos >= 0)
			{
				s_grid1.Put(iPos, 1, item->GetSize());
			}
			else
			{
				iPos = s_grid2.FindBlank(1, item->GetSize());

				if (iPos >= 0)
				{
					s_grid2.Put(iPos, 1, item->GetSize());
				}
				else
				{
					iPos = s_grid3.FindBlank(1, item->GetSize());

					if (iPos >= 0)
					{
						s_grid3.Put(iPos, 1, item->GetSize());
					}
					else
					{
						iPos = s_grid4.FindBlank(1, item->GetSize());

						if (iPos >= 0)
						{
							s_grid4.Put(iPos, 1, item->GetSize());
						}
						else
						{
							return false;
						}
					}
				}
			}
		}
	}

	return true;
}