SharePoint List and Data Transformations Authentication Errors

[Anonymous]

We discovered today that when making a connection to a SharePoint list and running certain data transformations it would continuously prompt for the users authentication and throw authentication errors.   We checked the SharePoint logs and noticed nothing was being passed and after troubleshooting found that it appears to be related to the number of columns in the list.

This particular list had 251 columns, connecting to it worked fine but adding unpivot or right outer join causes the authentication errors to appear.   Removing all but 5 columns from the query resolved the issue, so it appears that some data transformation can not handle large number of list columns.   

Anyone run in to this before?  The obvious workaround is to remove the columns that were not needed but wondering if there is a hard limit for data tranformations?