I happened to have a similar error. The bapi I'm using when creating a new material is BAPI_MATERIAL_SAVEDATA and I'm getting the following error:
Field LGTYP has been transferred inconsistently or is blank
LGTYP for MLGT is ""; previously ""
Acording to my functional user, the field LGTYP can be blank. He showed my on tx MM02.
Is there any missing field to be filled, or we are facing a config problem here?
Hope you can help me up here.