I have had similar problems with parts lists in drawings for iassemblies. I have never found out what causes the problem but I have found a way to fix it (temporarily). I have to open the iAssembly go to the BOM, disable the structured view, make a change to the file, undo the change, generate the files, go back to the BOM editor, enable the structured view, make a change to the file, undo the change to the file, generate all of the members again, open my master file that contains each member, save the file, open each drawing and delete the parts list, and then add the parts list back it. It is a huge time sink.
I don't know why it happens but I wish someone would let me know. I posted this issue a while back but I have not been given any feed back. It may be something I am doing but I don't know. I mentioned the fix is temporary because I have found that if I open the iAssembly and add a new member sometimes the problem shows up again.
Regards,
Nathan