This modification of Rome: Total War fixes the siege tower bug by replacing the graphic of large stone walls with the regular stone walls. The stats for the walls remain that of the large stone walls, so they are just as strong, just look like the smaller versions. Also, the siege tower is now the "small" one, with medium stats, and medium weapon. The arrow stats were also changed so the weapon fires from the right location on the siege tower. This should prevent the bug from ever happening again. Also, the fix for the epic walls is included in the descr_engine file, so you don't need to download that fix separately.