Just check if the Locator value in the "Stock Locators" FF Value Set is disabled or end dated.
Also check if only a particular locator is assigned to the suvinventory while associating a locator to a subinventory in the subinventory form.
Check the BOM that is having the component UL26300.
May be the locator specified on the BOM record is not valid anymore.
Try correcting the same using Discrete Job's Material Requirement Screen.
Similarly check if any supply locator is specified on WIP Parameters form, and check its validity.