Work-In-Progress inside a BOM

Why can’t I save new BOM when the assembly includes a finished item or goods-in-process or work-in-progress(WIP)?

I created a BOM for an WIP item flour mixture. Then when making the final product fried chicken, I included the WIP item in the recipe. However, the BOM would not save.

Yes, I can just breakdown the WIP, however, that is not the case in some products here.

Thank you.

First, look if the Item produced by the BOM has Include in Manufacturing checked in the Item DocType.

Second, In the Work Order entry, under Settings, UNCHECK (no check) Use Multi-Level BOM.
This will make the previous item (Flour) considered as one Item in the next BOM (chicken).

If this is checked, the ingredients for Flour will be those which will be retrieved. In my case, I usually Uncheck this checkbox so that my sub-parts are considered as one item in the Stock Entry Manufacturing movement records.