Issue changing element of an array

Can you share more of your code performing the save?  Is this within a button?  

Otherwise the a!save() expression you note above should not have any issues when used within a user interaction.

a!localVariables(
  local!array: {false,false},
  {
    a!richTextDisplayField(
      value: a!forEach(
        items: local!array,
        expression: {
          tostring(fv!item),
          char(13)
        }
      )
    ),
    a!buttonArrayLayout(
      align: "START",
      buttons: {
        a!buttonWidget(
          label: "Save",
          saveInto: a!save(local!array[1],true)
        )
      }
    )
  }
)