In "common-utils-input-submit" template of CMS plugin, the button is inserted in a <div class="button">

If "common-utils-input-submit" is override in a skin to remove this wrapper, the JS does not work anymore (a parent is expected)

See AmetysFormHelper#andleSubmitButton

$j("#submit-" + pos + "-" + id).parent().hide();            

$j("#form-next-" + pos + "-" + id).parent().show();