When reduction principle by Transaction - order is utilized and a company has both project based and non-project (stock) forecast, any sales order to the specified customer on the project forecast will reduce the forecast for the project.

In order to fix this, the reduction principle should include an option to indicate if the project is included in the reduction of the forecast. If selected YES then only lines where the project on the forecast line matches the project on the sales order line will reduce the project forecast.