Dataflow timeout on preview or "Save & Close"

Hi,

We have a desktop report that uses an ODBC connection and pulls data without fail.  When we try to move the SQL queries to dataflows (copying M-code from advanced editor), the dataflow always errors with the following timeout issue related to one or more entities.

Note that the gateway connection is successful and works fine - the error only occurs to longer-running queries.  The error message gives hardly any help as to the cause of the issue which we don't get using desktop.

Image when clicking "Save & Close":

Relates to following error on an entity:

Any ideas?

Thanks