Primefaces selectCheckboxMenu to update label when it is closed

Question

I am using primefaces 5.2. I have a<p:selectCheckboxMenu> within a <p:dataTable> for selecting multiple values. The label of the selectCheckboxMenu reads 'Select'. I want to update the label of the checkboxMenu to be 'Edit' if some value is selected or else keep it as 'Select' if nothing is selected. I want this to happen only after the selectCheckboxMenu is closed.

I referred the stackoverflow question How to update the label of p:selectCheckboxMenu without the component being closed after ajax call in primefaces?. But after selecting some value from the checkboxMenu, the menu blinks for a moment( ajax call happens and the label is updated) and it reapperars. But due to the blink happening in between , the behavior is weird. for eg. If I select the first checkbox within the menu, and then immediately second one, it blinks and when it reappears, only one checkbox would be checked. Here is the code snippet:

<p:column headerText="Apply To"  style="width:120px;text-align:center;">
    <p:selectCheckboxMenu id="applyToId" value="#{rule.accountTypes}" 
            label="#{rule.accountTypeLabel}" widgetVar="accntType">                                      
                <f:selectItems value="#{controller.customerAccTypes}" />
                    <p:ajax oncomplete="PF('accntType').show()"
                            listener="#{controller.populateLabel(rule,event)}"
                            update="applyToId"></p:ajax> 
    </p:selectCheckboxMenu></p:column>

The controller method:

public void populateLabel(NewRules rule,AjaxBehaviorEvent event) {
    if (rule.getAccountTypes().length == 0) {
        rule.setAccountTypeLabel("Select One"); 
    } else {
         rule.setAccountTypeLabel("Edit"); 
    }}

I am not sure if I am doing something wrong. Thanks in advance.