Cmd Batch Loader: 'Not a single item' error

I'm trying to load some data using the cmd batch loader tool for a number of different ItemTypes. When the script gets to the last ItemType, an error occurs in the cmd window that states "Not a single item" for each row of data to be imported. I ran into this issue when creating an onBeforeAdd server method for this ItemType. My workaround was to enclose the method's logic in a for-loop to iterate through each item individually. So there's no problem with adding these items manually through the Aras interface, but the batch loader still complains. Is there a fix I can make to the method itself? Or is there a way to change my batch script to get around this problem?