CasperJS: clicking checkbox not triggering events as it does in browser - casperjs

Question

I am trying to automate a process in CasperJS. However, I am facing some discrepancy between the behavior on a real browser vs the same in CasperJS.
Update: Process works fine with slimerJS but gives issue with headless
Here is my script:
var casper = require('casper').create({
"waitTimeout": 10000
});
var inputElements = {
"url": "http://www.jabong.com/incult-Tapered-Jeans-In-Indigo-1032119.html?pos=4",
"size": "34",
"address": {
"email": "someemail#xyz.com"
}
}
casper.options.viewportSize = {width: 1679, height: 902};
casper.start(inputElements.url, function (){
this.wait(10000, function (){
console.log("loaded");
})
});
var x = require('casper').selectXPath;
var sizeToSelect = inputElements.size;
// select size
casper.thenClick(x("//*[contains(#class,'size-desktop')]//"+
"li[contains(#class,'first') and contains(#class,'popover-options')]//"+
"span[contains(text(),'"+sizeToSelect+"')]/"+
".."));
// add to bag
casper.thenClick(x("//*[#id='add-to-cart']"));
// view cart
casper.thenClick(x("//*[#id='header-bag-sec']/a"))
// take a screenshot
casper.then(function() {
console.log("saving screenshot");
this.capture('../../1_view_cart.png');
});
casper.then(function() {
console.log('clicked ok, new location is ' + this.getCurrentUrl());
});
// place order
casper.then(function (){
this.click("[href='https://www.jabong.com/checkout/']");
})
// take a screenshot
casper.then(function() {
console.log("saving screenshot");
this.capture('../../2_address_details.png');
});
casper.then(function (){
this.sendKeys("#login-email", inputElements.address.email);
})
casper.then(function (){
this.click("#do-guest-checkout");
});
// take a screenshot
casper.then(function() {
console.log("saving screenshot");
this.capture('../../3_guest_checkout.png');
});
casper.waitFor(function check() {
return this.evaluate(function() {
return document.querySelector('#btn-login-checkout').textContent == "Continue as Guest";
});
}, function then() {
this.click('#btn-login-checkout');
});
casper.run();
On the last page, clicking on checkbox "Checkout as Guest" on a browser removes the password input field and changes the text of the Login button to "Continue as Guest". Attached screenshot:
However, in CasperJS, the password input field and the Login button are not changing. Any idea what am I doing wrong ?