WHEN-NEW-ITEM-INSTANCE - on a Oracle seeded Form Vs WHEN-NEW-ITEM-INSTANCE on the same item in CUSTO

I have a WHEN-NEW-ITEM-INSTANCE at the ITEM level on a Oracle EBS seeded form / block which uses POPULATE_GROUP_WITH_QUERY with a dynamically built query (from TABLE A, column 1 and column 2) and assigning to a seeded LOV.
On the same exact form, block and item, I also have a CUSTOM.pll code which has the 'WHEN-NEW-ITEM-INSTANCE' doing the CREATE_GROUP_FROM_QUERY building a dynamic SQL query (from TABLE X, column 1 and column 2) and assigning to custom Record Group and to the same seeded LOV.

The form all the time shows up the Oracle EBS seeded qurery results but not showing the values from the CUSTOM.pll code. Any ideas and suggestions on how to override the seeded list of values with my custom ones ?