SOLVED
It turns out that the 3 label reports in question had grouping criteria defined that were just doing sorts yet the code was setting the orderon property to implement the sorts. Not something I was expecting for mailing labels.
I also found that MS Access was not sending the same...
I am tasked with converting an old MS Access Application to a MS Access front end and SQL Server back end. I have several reports (all labels) which are giving me an SQL Server ODBC error when I open them in preview mode but which open fine in report mode.
This command fails...