The system module that is used in the SUM should have share same list (level) as the source module of the data so that Anaplan can lookup the property of the list item. The SYS04 module that is used might not be at the same level as the INV01 module.
Still very confused. I created a Line Item that would have the same list as the source, but still contain my Distribution Center information (G3), but still giving me a error with the formula below. Please advice.
'INV01 Inventory Ordering'.Safety Stock Exception Count[SUM:'SYS07 Distribution Center Details'.Distribution Center]