MS Access – Fixing Form and Subform Interaction Issues

There is a main form bound to the main table, public_OUT_Detalle_PMC. And there is a form bound to a smaller table, public_ficha_negocio, which is a selection of fields in the bigger table. This second form is used as a subform, and I want to save the edits made to the subform onto the main table.

I have tried to use a simple SQL Update query, but for some unkown reason I can't make it work and it is driving me crazy.

    Dim db As DAO.Database
    Dim qdfFN As DAO.QueryDef
    Dim rsFN As DAO.Recordset
    Set db = CurrentDb
    Set qdfFN = db.CreateQueryDef("")
    qdfFN.sql = "select * from [public_ficha_negocio] where [Codigo_RQM_Necesidad]='" & Me.Codigo_filtro.value & "';"
    qdfFN.ReturnsRecords = True
    Set rsFN = qdfFN.OpenRecordset
    Dim qdf As DAO.QueryDef
    Dim sSQL As String
    sSQL = "UPDATE [public_OUT_Detalle_PMC] SET " & _
              {a lot of fields are updated, I cut them out of the paste for simplicity}
              "WHERE [public_OUT_Detalle_PMC].[Codigo_RQM_Necesidad] = '" & rsFN!Codigo_RQM_Necesidad & "');"
    Set qdf = db.CreateQueryDef("", sSQL)
    qdf.Execute dbFailOnError
    qdf.Close
    qdfFN.Close
    rsFN.Close
    Set qdfFN = Nothing
    Set rsFN = Nothing
    Set qdf = Nothing

The query qdfFN is used to retrieve the record of the smaller table which data I want to "passthrough" to the bigger table. The query qdf is the one that, either doesn't work or I am not understanding how to use these vba objects.

I have used Debug.print to check the values of rsFN and they are correct, I mean, the values I want to pass onto the bigger table are there! This is cracking my head