Thanks to adamepp’s discovery, I added this to my functions file and fixed it:
// Fix Advanced Custom Fields and Visual Composer CSS conflict
function afc_vc_fix() {
echo '
<style>
.repeater .row:before,
.repeater .row:after {
display: auto;
content: none;
}
</style>';
}
add_action('admin_head', 'afc_vc_fix');