Multiple checkbox in a Grid.

Hello.

I'm creating an interface but I have a problem because I want select a checkbox for every row I wish to delete.

I select the first one, but when I select the second one the first one is unselected.

{
  a!gridLayout(
    
    headerCells: {
      a!gridLayoutHeaderCell(label: "", align: "CENTER"),
      a!gridLayoutHeaderCell(label: "Precio de Colocación", align: "CENTER"),
      a!gridLayoutHeaderCell(label: "Número de Títulos", align: "CENTER"),
      a!gridLayoutHeaderCell(label: "Importe", align: "CENTER"),
      a!gridLayoutHeaderCell(label: "Casa de Bolsa", align: "CENTER"),
      a!gridLayoutHeaderCell(label: "Tipo de Registro", align: "CENTER")
    },
    columnConfigs: {
      a!gridLayoutColumnConfig(weight: 1),
      a!gridLayoutColumnConfig(weight: 2),
      a!gridLayoutColumnConfig(weight: 2),
      a!gridLayoutColumnConfig(weight: 2),
      a!gridLayoutColumnConfig(weight: 1),
      a!gridLayoutColumnConfig(weight: 1)
    },
    rows: {
      a!forEach(
        items: ri!colocacion,
        expression: {
          a!gridRowLayout(
            contents: {
              a!checkboxFieldByIndex(
                choiceLabels: "",
                saveInto: {ri!checkbox},
                align: "CENTER"
              ),
              a!floatingPointField(
                align: "CENTER",
                value: index(fv!item, "precioColocacion", null),
                saveInto: fv!item.precioColocacion
              ),
              a!floatingPointField(
                align: "CENTER",
                value: index(fv!item, "numeroTitulos", null),
                saveInto: fv!item.numeroTitulos
              ),
              a!floatingPointField(
                align: "CENTER",
                value: index(fv!item, "importe", null),
                saveInto: fv!item.importe
              ),
              a!dropdownField(
                value: index(fv!item, "casaBolsa", null),
                saveInto: fv!item.casaBolsa,
                choiceLabels: "ACTIN",
                choiceValues: "ACTIN",
                placeholder: "Seleccione"
              ),
              a!dropdownField(
                value: index(fv!item, "tipoRegistro", null),
                choiceLabels: "ACTIN",
                choiceValues: "ACTIN",
                placeholder: "Seleccione",
                saveInto: fv!item.tipoRegistro,
              )
            }
          )
        }
      ),
      a!gridRowLayout(
        contents: {
          a!richTextDisplayField(
            
          ),
          a!richTextDisplayField(

          ),
          a!richTextDisplayField(
            align: "CENTER",
            value: if( isnull(index( ri!colocacion, "importe", null)), null, sum(ri!colocacion.numeroTitulos))
          ),
          a!richTextDisplayField(

          ),
          a!richTextDisplayField(

          ),
          a!richTextDisplayField(

          ),
        }
      )
    }
  ),
  a!buttonArrayLayout(
    align: "CENTER",
    buttons: {
      a!buttonWidget(
        label: "Agregar",
        submit: true,
        saveInto: {
          a!save(ri!colocacion, append(ri!colocacion, 'type!{urn:com:appian:types:BMV}BMV_colocacion'()))
        },
        style: "NORMAL",
      ),
      a!buttonWidget(
        label: "Eliminar",
        submit: true,
        style: "DESTRUCTIVE",
        saveInto: a!save(ri!colocacion, remove(ri!colocacion, ri!checkbox))
      )
    }
  )
}