Hi, your problem might be caused by multiple reasons:
1. Monsters are set to drop a specific item in mob_proto, that specific item can be find on the drop_item row from each monster. (0 is default)
Now, it would make no sense for you to look over each monster to remove that item, anyway this is not the case. The item drops with one condition, if etc_drop_item.txt is filled has that vnum, that's where the item get's it's chance to drop and it's the same for every monster that has
I have a problem on the server with the drop, some players drop items that are not in mob_drop_item or common_drop_item, I want to mention that in mob_drop_item I have some items with a 1000% chance of drop, but those items that fall on the ground are nowhere the drop.
ex: players drop some knifes for ninja or fans for sham