Has anyone encountered this error before? Master default is false on the BOM and I don't see any such this as Item default.

Any chance its the default for location on an inactive item and the check isn't correctly looking for that?

Ya, it took me a minute but I think I get it. Have to null the default location multiselect and mark master default false on the assembly first.

They don't make that information easily attainable or consistent between query and search, its quite a pita