I have not made any changes to the Objlist.txt. I would not know how. I would have to check to see if it happens to the Original MM7 that has no modifications. To add that feature, I will need to edit the Monsters.txt file and add under Special "Summon,air,Bat A".The summon effect is what's causing the crash. Have you changed spells in Data\Tables\ObjList.txt? Would it happen if you just give gargoyles summon in the regular MM7 + my patch?
Update: The Gargoyles are the ones that summon bats in Maestro's mod and cause the crash. I gave the gargoyles the summon bat spell in the original MM7, but they do not summon anything, therefor the game does not crash. Is there another file that needs to be edited other then monsters.txt?