Why Am I Getting Two Different Results From One Constant Source?

Anonymous,

You may try using the try expression in a recursive function.

Thanks again v-chuncz-msft. This seems to be working okay:

let
  GetData = () => if List.Contains(Table.ColumnNames(Web.Page(Web.Contents("https://webapps.MyDomain/path/req_search.cfm?page=AP")){1}[Data]), "Details") then 
    Table.RemoveColumns(Web.Page(Web.Contents("https://webapps.MyDomain/path/req_search.cfm?page=AP")){1}[Data],{"Details"}) else @GetData(),    
  ShowData = GetData()
in
  ShowData

v-chuncz-msft, I went back and changed my query to use try-otherwise, with the recursive function structured as below, and it worked this way too. So I'm marking your original response as a solution. Thanks yet again for your help.

let
  GetData = () => try Table.RemoveColumns(Web.Page(Web.Contents("https://webapps.MyDomain/path/req_search.cfm?page=AP")){1}[Data],{"Details"}) otherwise @GetData(),
  ShowData = GetData()
in
  ShowData