Cascading lov fails with wrong number of columns

Hi,

Using apex 19.2.

Have an Interactive Grid form in which I want to use a cascading LOV.

The IG has 2 items called EXPED_CD and STATION_NUM.

In the IG form I have set EXPED_CD as a Popup LOV that has a type of SQL Query.

It is populated using the query: select distinct(exped_cd) from test_tab1 order by exped_cd;

This works fine. I can hit the add row button in the IG and see a list of values to select from.

Now, I am trying to configure the STATION_NUM item as a cascading lov.