Evaluation error in dataflow

Advanced editor code

let

  Source = SharePoint.Files("https://wincanton.sharepoint.com/sites/HDAnalytics", [ApiVersion = 15]),

  #"Filtered rows" = Table.SelectRows(Source, each [Folder Path] = "https://wincanton.sharepoint.com/sites/HDAnalytics/Shared Documents/HDx Sources/Delivery Outcome Report/"),

  #"Filtered hidden files" = Table.SelectRows(#"Filtered rows", each [Attributes]?[Hidden]? <> true),

  #"Invoke custom function" = Table.AddColumn(#"Filtered hidden files", "Transform file (4)", each #"Transform file (4)"([Content])),

  #"Renamed columns" = Table.RenameColumns(#"Invoke custom function", {{"Name", "Source.Name"}}),

  #"Removed other columns" = Table.SelectColumns(#"Renamed columns", {"Source.Name", "Transform file (4)"}),

  #"Expanded table column" = Table.ExpandTableColumn(#"Removed other columns", "Transform file (4)", Table.ColumnNames(#"Transform file (4)"(#"Sample file (4)"))),

  #"Changed column type" = Table.TransformColumnTypes(#"Expanded table column", {{"Source.Name", type text}, {"Column1", type text}, {"Column2", type text}, {"Column3", type text}, {"Column4", type text}, {"Column5", type text}, {"Column6", type text}, {"Column7", type text}, {"Column8", type text}, {"Column9", type text}, {"Column10", type text}, {"Column11", type text}, {"Column12", type text}, {"Column13", type text}, {"Column14", type text}, {"Column15", type text}, {"Column16", type text}, {"Column17", type text}, {"Column18", type text}, {"Column19", type text}, {"Column20", type text}, {"Column21", type text}, {"Column22", type text}, {"Column23", type text}, {"Column24", type text}, {"Column25", type text}, {"Column26", type text}, {"Column27", type text}, {"Column28", type text}, {"Column29", type text}}),

  #"Promoted headers" = Table.PromoteHeaders(#"Changed column type", [PromoteAllScalars = true]),

  #"Changed column type 1" = Table.TransformColumnTypes(#"Promoted headers", {{"Week 35.csv", type text}, {"Contract ID", type text}, {"Order Code", type text}, {"OrderCode2", type text}, {"Retailer", type text}, {"Retailer Ref", type text}, {"Surname", type text}, {"PostCode", type text}, {"Outbase", type text}, {"Visit Type", type text}, {"Visit Date", type text}, {"Arrival Time", type time}, {"Departure Time", type time}, {"Planned Time On Site", Int64.Type}, {"Date Entered", type text}, {"SKU", type text}, {"SKU Long Description", type text}, {"Debrief Code", Int64.Type}, {"Debrief Code Description", type text}, {"Route Number", Int64.Type}, {"Consignment Number", type text}, {"Stock With Customer", type text}, {"SKU Cartons", Int64.Type}, {"SKU Cube (Volume)", type number}, {"SKU Dwell Hierarchy", type text}, {"SKU Delivery Service Time", Int64.Type}, {"SKU Collection Service Time", Int64.Type}, {"SKU Install Service Time", Int64.Type}, {"Supplier Code", Int64.Type}, {"Supplier Description", type text}}),

  #"Changed column type with locale" = Table.TransformColumnTypes(#"Changed column type 1", {{"Visit Date", type date}}, "en-GB"),

  #"Changed column type with locale 1" = Table.TransformColumnTypes(#"Changed column type with locale", {{"Date Entered", type date}}, "en-GB"),

  #"Removed errors" = Table.RemoveRowsWithErrors(#"Changed column type with locale 1", {"Visit Date"}),

  #"Renamed columns 1" = Table.RenameColumns(#"Removed errors", {{"Week 35.csv", "Source"}}),

  #"Added custom" = Table.AddColumn(#"Renamed columns 1", "LookUp Ref", each [Order Code] & [PostCode] & Date.ToText([Visit Date],"dd/MM/yy")),

  #"Transform columns" = Table.TransformColumnTypes(#"Added custom", {{"LookUp Ref", type text}}),

  #"Replace errors" = Table.ReplaceErrorValues(#"Transform columns", {{"LookUp Ref", null}}),

  #"Filtered rows 1" = Table.SelectRows(#"Replace errors", each [Outbase] <> "Channel Islands"),

  #"Sorted rows" = Table.Sort(#"Filtered rows 1", {{"LookUp Ref", Order.Ascending}, {"Debrief Code Description", Order.Descending}}),

  #"Added index" = Table.AddIndexColumn(#"Sorted rows", "Index", 0, 1, Int64.Type),

  #"Added index 1" = Table.AddIndexColumn(#"Added index", "Index (2)", 1, 1, Int64.Type),

  #"Merged queries" = Table.NestedJoin(#"Added index 1", {"Index"}, #"Added index 1", {"Index (2)"}, "Added index 1", JoinKind.LeftOuter),

  #"Expanded Added index 1" = Table.ExpandTableColumn(#"Merged queries", "Added index 1", {"LookUp Ref"}, {"LookUp Ref.1"}),

  #"Renamed columns 2" = Table.RenameColumns(#"Expanded Added index 1", {{"LookUp Ref.1", "Prev Look Up"}}),

  #"Added custom 1" = Table.AddColumn(#"Renamed columns 2", "Count", each if [Prev Look Up] = [LookUp Ref] then 0 else 1),

  #"Removed columns" = Table.RemoveColumns(#"Added custom 1", {"Index", "Index (2)", "Prev Look Up"}),

  #"Transform columns 1" = Table.TransformColumnTypes(#"Removed columns", {{"Count", type text}}),

  #"Replace errors 1" = Table.ReplaceErrorValues(#"Transform columns 1", {{"Count", null}}),

  #"Added custom 2" = Table.AddColumn(#"Replace errors 1", "Client_Depot", each [Contract ID] & [Outbase]),

  #"Transform columns 2" = Table.TransformColumnTypes(#"Added custom 2", {{"Client_Depot", type text}}),

  #"Replace errors 2" = Table.ReplaceErrorValues(#"Transform columns 2", {{"Client_Depot", null}})

in

  #"Replace errors 2"