Radio Group Multiple Update

I have repeating rows, at the end of which is a radio group button for a user to select only one of those records. Once submit is clicked, the database should update all of those rows of any changes made. For example, if row 2 is 'default' and user wants to choose row 6 as 'default', the database should update those records to indicate only row 6 is now selected as 'default'.

Before I add the multiple update, the selection process works just fine. However, once I add the multiple update, when row 2 shows as 'default' and the user selects row 6 to be 'default', row 2 remains selected along with row 6. Once the submit button is pressed, all records are updated to be selected.

I have attached the file and appreciate any help you can offer.