Bug: Table.ReplaceValue kills all column types

ImkeFI got into the same problem and I solved it by using this function that I found here:

Say you have a function called revert_column_types defined as below:

(baseTable as table, processedTable as table) =>
let
    baseTableType = Value.Type(baseTable),
    CommonColumnNames = List.Intersect({Table.ColumnNames(baseTable), Table.ColumnNames(processedTable)}),
    processedTableNewColumnTypes = 
        List.Transform(
            CommonColumnNames, 
            each {_} & {Type.TableColumn(baseTableType, _)}
        ),
    appliedColumnTypes = Table.TransformColumnTypes(processedTable, processedTableNewColumnTypes)
in
    appliedColumnTypes

Now in your code you can do this:

// let's assume old_table is the original table with all the right column types
// now you do some crazy things like new_table = Table.ReplaceValue(old_table, ...)
// all you need to do after is to call that function above
result = revert_column_types(old_table, new_table)

I arrived at this solution after a day of trial/error and that finally worked for me. Hope it helps, too.