Invalid Location Reference Key on Item Supply Plan

We are a manufacturing firm using Advanced Manufacturing, Demand Planning and Distribution Networks. For a new outsource manufacturing project, we had cause to enter a new Location. In the process, a Location was entered, then deleted. Now when we run Generate Item Supply Plan (which never provides helpful error messages), it is failing with, "Invalid location reference key 36 for subsidiary 2". In the sequence of assignment of Location Internal IDs, 36 would have been the one that was deleted. However, that location was never (knowingly) used anywhere, so, in theory, nothing should be referencing it, but obviously something is