Table.TransformColumnNames seems to turn Records into Lists - this code previously didn't do this

Hi I've been using this line of code to rename the columns of a JSON nested table for years - all of a sudden it has stopped working and now when I run it it converts all of the RECORDS in the column to LISTS.  I feel it is either a bug or a really simple solution.

= Table.TransformColumnNames(#"Expanded Column1.fields", each #"Lookup Function"(Text.BeforeDelimiter(_,"."),Text.AfterDelimiter(_,"."),JiraFields,"Column1.id","Column1.name"))

The error message returns on subsequent steps, which would have formerly expanded the Records into Tables

Expression.Error: We cannot convert the value "[List]" to type Table.
Details:
Value=[List]
Type=[Type]