After load form and the first running function in the 'events > change' in the select field the validation stops work

[typo3ua]

I have simple form...

$(document).ready(function() { 
    var data = {
        "actionReal": "One or Two",
        "firstName": "First Name",
        "lastName": "Last Name"
    };
    var schema = {
        "title":"Form title",
        "type":"object",
        "properties": {
            "actionReal": {
                "type": "string",
                "required": true,
                "default": "none"
            },
            "firstName": {
                "required": true
            },
            "lastName": {
                "required": true
            }
        }
    };
    var options = {
        "fields": {
            "actionReal": {
                "type": "select",
                "label": "Your action",
                "noneLabel": "Select action...",
                "dataSource": [
                    {
                        "value": "one",
                        "text": "Action One"
                    },
                    {    
                        "value": "two",
                        "text": "Action Two"
                    }
                ],
                "events": {
                    "change": function() {
                        var firstName = this.parent.childrenByPropertyId["firstName"],
                            lastName = this.parent.childrenByPropertyId["lastName"];
                        actionReal = this.getValue();
                        if (actionReal === 'one') {
                            firstName.options.label = "First Name Action One";
                            lastName.options.label = "Last Name Action One";
                        } else {
                            firstName.options.label = "First Name Action Two";
                            lastName.options.label = "Last Name Action Two";
                        }
                        firstName.refresh();
                        lastName.refresh();
                    }
                },
                "removeDefaultNone": false,
                "validate": true
            },
            "firstName": {
                "type": "text",
                "label": "First Name Action Two",
                "validate": true
            },
            "lastName": {
                "type": "text",
                "label": "Last Name Action Two",
                "validate": true
            }
        },
    };
    $("#form").alpaca({
            "data": data,
            "schema": schema,
            "options": options,
            "type": "create"
    });
});

When I selected in the field Your action the value Action one the validation stops work, but when I selected in the field Your action another value then the validation works well... Can someone tell me what is wrong in my form?

Guys I need your help in resolve the issue, please.