If you are seeing more than one button, than you included the button as part of the repeat region. The button should not be added as part of the repeat region, it should be outside the repeat region.
It sounds to me like you are either including the entire form as the repeat region, or the button in the repeat region. Only the fields that should be updated should be included in the repeat region.
The multiple update cannot work directly from a recordset, it is not set up to loop through a recordset, it is set up to loop through a collection of form elements.