Additional Material attachment in OPIM

We use Additional Material to represent some special items, for example,  insulation kit gasket. However, in OPIM by default, additional material just showing in iso image like a message text and it is not listed in BOM. By adding an ADDITIONAL_MATERIAL class in Isometrics Isoextractor schema, currently, additional material item is listed in BOM now but always under Field Materials, also Part ID of it display randomly in ISO image - some times in the air, some times no where.

Anyone know a fixed of it?