DataSource.Error List.Accumulate

I think I have it! 
For other people, this code:
Takes a sharepoint folder

• Filter excels by name
• Depending on the File name takes different sheets
• Finally combine all data on one table.

Here is the code:

let
FolderUrl = "sharepoint folder",

//Get the list of files from SharePoint
Source = SharePoint.Files("sharepoint", [ApiVersion = 15]),

//Filter the files to select only those starting with "A" or "B"
FilteredFiles = Table.SelectRows(Source, each Text.StartsWith([Name], "A") or Text.StartsWith([Name], "B")),

//Define a function to load data from each Excel file
LoadData = (file as text) =>
let
//Fetch the binary content of the Excel file
ExcelContent = Web.Contents(FolderUrl & file),

//Load the Excel workbook
ExcelWorkbook = Excel.Workbook(ExcelContent),

//Determine the sheet name based on the file name
DataSheetName =
if Text.StartsWith(file, "A") then "C"
else if Text.StartsWith(file, "B") then "D"
else null,

//Extract data from the specified sheet
DataSheet = if DataSheetName <> null then ExcelWorkbook{[Item=DataSheetName, Kind="Sheet"]}[Data] else null,

//Skip the first row if data exists
SkipFirstRow = if DataSheet <> null then Table.Skip(DataSheet, 1) else null,

//Add a column to identify the source file
AddSourceColumn = Table.AddColumn(SkipFirstRow, "FileSource", each file, type text)
in
//Return the resulting table
AddSourceColumn,

//Apply the LoadData function to each file and combine the results
CombinedData = Table.Combine(List.Transform(FilteredFiles[Name], each LoadData(_)))
in
CombinedData