Value cannot be null. Parameter name: evaluation - Amazon Redshift

I still have the issue. I deleted/reinstalled PBI, still have the issue.  Server and credentials are correct. When I create a new query and attempt to put custom SQL in the step I get the error.
However, I have found a workaround:

• Create a new blank PBIX
• Open Power Query Editor, create a new Query
• Enter Amazon Redshift server and database name
• Enter credentials if needed
• Select an existing dataflow
• Leave it as DirectQuery, not Import
• Query creates successfully
• Return to the first Applied Step ("Source") in the Query and update it, inserting the SQL command
• Delete the "Navigation" Applied Step

This gives me the query I want. I repeated this step four times to give me four queries, each based on custom SQL.

I still don't know why it fails when I do it the first way.

I would love to attach the error log, but that doesn't seem to be an option here.