Wicket Strange behaviour of URL with ajax

Question

I have issue that have strange steps. I have ajax behave rendered on Head render stage

    final AbstractDefaultAjaxBehavior behave = new AbstractDefaultAjaxBehavior() {
       protected void respond(final AjaxRequestTarget target) {
             boolean undoEn = getRequest().getQueryParameters().getParameterValue("undoEn").toBoolean();
             if (undoEn) {
                mSaveButton.setEnabled(true);
                target.add(mSaveButton);
             }
        }
    };

    public String getCallbackName() {
        return "saveButtonVisibilityToggle";
    }

    @Override
    public void renderHead(IHeaderResponse response) {
        String script = getCallbackName() + " = function (e) {  Wicket.Ajax.ajax({\"u\": \"" + behave.getCallbackUrl() + " + &undoEn=\"+e+\"\" });}";
        response.render(OnDomReadyHeaderItem.forScript(script));
    }

Everything works well this behave called every time node changed in tinyMCE editor

     settings.addCustomSetting(" setup: function(editor) {" +
            "        editor.on('NodeChange', function(e) {" +
            " editor.save();" +
            getCallbackName() + "(editor.undoManager.hasUndo())" +
            "        });" +
            "    }");

But sometimes when i leave browser tab, change few tabs (chrome) then use other app for few minutes, and turn back to our tab, ajax url have accidently appeared in browser url.

http://localhost:8080/wicket/bookmarkable/com.tac.kulik.pages.SomePage?3-1.IBehaviorListener.0-contentPanel&entityId=2+++&undoEn=true

this is also quite strange that instead normap parameter pass it's ++++ signs added

by the way this sighns recognized as "2 " so for some reason '+' changed to whitespace

UPDATE 1 Using @svenmeier answer i've page start's infinite loop refreshing. with logs

org.apache.wicket.core.request.mapper.StalePageException: A request to     
page '[Page class = x.x.x.CardPage, id = 25, render count = 1]' has been
 made with stale 'renderCount'. The page will be re-rendered.

and really for some reason behave link has renderCount 1, but form has 0. the request from browser jquery-1.12.4-ver-1476216952000.js:10254 XHR finished loading: GET "http://localhost:8080/wicket/bookmarkable/com.tac.pages.ca…?4-0.IBehaviorListener.0-contentPanel&cardId=1&_=1476873175645&undoEn=true"

I ve add some set of JS to prevent cicling refreshing, But i'we still has Stale exception

     "if (editor.undoManager.hasUndo()) { " +
            "                  console.debug('Behave called ');" +
            behave.getCallbackScript() +
            "        }" +

this is my behave

   final AbstractDefaultAjaxBehavior behave = new AbstractDefaultAjaxBehavior() {
        protected void respond(final AjaxRequestTarget target) {
            log.info("Behave called");
            boolean undoEn = getRequest().getQueryParameters().getParameterValue("undoEn").toBoolean();
            if (undoEn) {
                mSaveButton.setEnabled(true);
                target.add(mSaveButton);
            }
        }
        //
        @Override
        protected void updateAjaxAttributes(AjaxRequestAttributes attributes) {
            super.updateAjaxAttributes(attributes);
            String undoEn = "return {'undoEn': editor.undoManager.hasUndo()};";
            attributes.getDynamicExtraParameters().add(undoEn);
        }
    };

And there is no difference, it could be behave without any realization, page behaviour the same((

    final AbstractDefaultAjaxBehavior behave = new AbstractDefaultAjaxBehavior() {
        @Override
        protected void respond(AjaxRequestTarget target) {

        }
    };

Answer 1

You should rework your behavior to use dynamic extra parameters instead.

@Override
protected void updateAjaxAttributes(AjaxRequestAttributes attributes)
{
    super.updateAjaxAttributes(attributes);

    String undoEn = "return {'undoEn': editor.undoManager.hasUndo()}";
    attributes.getDynamicExtraParameters().add(undoEn);
}

And:

settings.addCustomSetting(
        "setup: function(editor) {" +
        "  editor.on('NodeChange', function(e) {" +
        "    editor.save();" +
        "    " + getCallbackScript() + ";" +
        "  });" +
        "}");