When you applied the repeat selection server behavior to the page did you apply it to the entire form? The repeat selection should be only applied to the fields in the form that you need to make use of in the multiple update or delete. If the button or any other part of the form were selected when applying this server behavior this is the result that would occur. Please let me know about this and if there are issues that you are finding and I can do some tests like you are doing to see if there is a problem.