AD table definition shows a default value for m_inventoryline.locator_id as the default locator read at login .. which may be in a warehouse in Org 1
If a user creates an Internal Use Inventory for a warehouse in Org 2 and then fails to select a Locator in the line, the record will save and default in the Locator from Org1 warehouse. This will then display as null because the dynamic validation filters it out. It should display either no Locator or the default for the warehouse selected at Inventory header doc level.
A solution is to set the default value on the Locator column to -1 ... but a more robust solution may be worthwhile.