This page "Drills Down" to EMPTY FIELDS. The Production BOM and Routing tables are NOT read before linking.

The fix is below. Microsoft error in italics, correction in bold.

        field("RoutingNo."; Rec."Routing No.")

        {

          ApplicationArea = Manufacturing;

          Lookup = false;

          ToolTip = 'Specifies the production route that contains the operations needed to manufacture this item.';

          trigger OnDrillDown()

          var

            RoutingHeader: Record "Routing Header";

          begin

            // if RoutingHeader."No." <> '' then

            //  RoutingHeader.SetRange("No.", Rec."Routing No.");

            If Rec."Routing No." <> '' then begin

              RoutingHeader.SetRange("No.", Rec."Routing No.");

              Page.Run(Page::Routing, RoutingHeader);

            end;

          end;

        }

        field("ProductionBOMNo."; Rec."Production BOM No.")

        {

          ApplicationArea = Manufacturing;

          Lookup = false;

          ToolTip = 'Specifies the production BOM that is used to manufacture this item.';

          trigger OnDrillDown()

          var

            ProductionBOMHeader: Record "Production BOM Header";

          begin

            // if ProductionBOMHeader."No." <> '' then

            // ProductionBOMHeader.SetRange("No.", Rec."Production BOM No.");

            if Rec."Production BOM No." <> '' then begin

              ProductionBOMHeader.SetRange("No.", Rec."Production BOM No.");

              Page.Run(Page::"Production BOM", ProductionBOMHeader);

            end;

          end;

        }