I also had this problem, I found the answer to be in the included javascript of the repeater field (acf-repeater/js/input.js).
At the end of input.js there is this part:
$(document).on('mouseenter', '.repeater tr.row', function( e ){
// vars
var $el = $(this).find('> td.remove > a.acf-button-add'),
margin = ( $el.parent().height() / 2 ) + 9; // 9 = padding + border
// css
$el.css('margin-top', '-' + margin + 'px' );
});
$(document).on('acf/conditional_logic/show acf/conditional_logic/hide', function( e, $target, item ){
// Makes shit crappy slow
$target.closest('tr.row').trigger('mouseenter');
});
Just comment it out, and everything is fast again.
