Ignoring error in Table.ExpandTableColumn or auto-replace with null

Hi Hamster0406, try this - it works with sample, but maybe it won't with real data:

Result

You can delete whole Transform File Group and replace code of your Tally ETL Issue query with this code:

let
    Source = Folder.Files("C:\Users\Yashw\OneDrive\Email attachments\Tally ETL Issue\"),
    FilteredRows = Table.SelectRows(Source, each ([Extension] = ".xml")),
    BinaryToTable = Table.TransformColumns(FilteredRows, {{"Content", Xml.Tables}}),
    Ad_Transform = Table.AddColumn(BinaryToTable, "Transform", each 
        [ t1 = [Content]{1}[Table],
          t2 = t1{1}[Table],
          t3 = t2{0}[Table],
          t4 = t3{0}[Table],
          ExpandedColumns = List.Accumulate(Table.ColumnNames(t4), t4,
                (s,c)=> try Table.ExpandTableColumn(s, c, Table.ColumnNames(Table.Column(s, c){0}), List.Transform(Table.ColumnNames(Table.Column(s, c){0}), (x)=> c & "|" & x)) otherwise s),
          Ad_SourceName = Table.AddColumn(ExpandedColumns, "SourceName", (x)=> [Name]),
          Reordered = Table.ReorderColumns(Ad_SourceName, {"SourceName"} & Table.ColumnNames(ExpandedColumns))
        ][Reordered], type table),
    CombinedAllFiles = Table.Combine(Ad_Transform[Transform])
in
    CombinedAllFiles