markup not found on feedback panel (wicket 7.4)

Hi, On one application we are getting sporadic errors like org.apache.wicket.markup.MarkupNotFoundException: Markup not found for Component: [FencedFeedbackPanel [Component id = feedback]] at org.apache.wicket.Component.internalRender(Component.java:2348) at

how to restrict the feedback message to display only one time for FormComponentPanel

our app has a phone number field like ###-###- x## on the page We define a phone number class as FormComponentPanel in our app like below public class PhoneFormComponent extends FormComponentPanel {