One-Page Checkout [Support Thread]

[lat9]

I'm following up on a post from several weeks ago. Client just approved installing the current version. I have 2.3.8 installed and getting the same error I was before when clicking update for the address section in guest checkout:

setFormSubmitButton, payment-module: null
jquery.checkout_one.js?1618668915:54 Showing "confirm"
jquery.checkout_one.js?1618668915:54 Setting orderConfirmed (0), submitter (null)
jquery.checkout_one.js?1618668915:54 jQuery version: 1.7.1
jquery.checkout_one.js?1618668915:54 saveCustomerInfo, starts ...
index.php?main_page=checkout_one:58 {cache: false, type: "POST", traditional: true, dataType: "json", timeout: 5000,##…}
jquery.checkout_one.js?1618668915:998 Uncaught TypeError: Cannot read property 'length' of null
at Object.<anonymous> (jquery.checkout_one.js?1618668915:998)
at n (jscript__jquery.min.js:2)
at Object.fireWith (jscript__jquery.min.js:2)
at Object.fire [as resolve] (jscript__jquery.min.js:2)
at Object.success (index.php?main_page=checkout_one:66)
at n (jscript__jquery.min.js:2)
at Object.fireWith [as resolveWith] (jscript__jquery.min.js:2)
at w (jscript__jquery.min.js:4)
at XMLHttpRequest.d (jscript__jquery.min.js:4)

Zen Cart 1.5.7a
PHP 7.2

I did copy the one extra file in /includes/modules/pages/checkout_payment to /includes/modules/pages/checkout_one. It was: jscript_double_submit.php

You need to upgrade to a now-extant version of jQuery. Current version is 3.6.0; zc157c ships with 3.5.1.