Old MRP tries to run the MRP calculation in the right BOM level sequence by calculating BOM levels prior to running the MRP.
However, New MRP Solutions has experienced that it is not possible to calculate the right BOM level in a number of situations. A situation could be manufacturing company that have factories in more than one country.
The level problem arises if one of the factories produces a component used in finished products in several factories because the right component level consequently changes depending on the factory that produces the finished product.
Old MRP runs and completes the MRP calculation company after company. The result is that the component item must be MRP updated more than once during a complete inter-company MRP that also results in that the used BOM level order in the first MRP calculated company by definition was wrong.
The problems with the faulty planned order typical occurs the second time the MRP runs and updates an item as existing receipts and on-hand stock levels have already been used to fulfill demands in the first MRP run.