Diagnosis -Confirmed:The checkout fails with HTTP 500 immediately after a customer selects a shipping method. -Confirmed:A JavaScript error also occurs during checkout. -Confirmed:The available evidence does not include the server-side PHP error, exception, stack trace, failing request, or response body. -Likely:The HTTP 500 indicates a server-side failure triggered during the shipping-method update or checkout processing. The JavaScript error may be a frontend symptom caused by the failed server response. -Unknown:The responsible plugin, theme customization, WooCommerce callback, shipping integration, or custom code cannot yet be identified from the supplied evidence. -Not established:There is currently insufficient evidence to attribute the failure specifically to Stripe Payments, WooCommerce Shipping, LiteSpeed Cache, Astra, PHP 8.3, or WooCommerce itself. Fix Plan -Required Fix:Do not modify PHP, JavaScript, shipping configuration, payment configuration, or caching yet. -Required Diagnostic:Capture the exact server-side error generated when the shipping method is selected. -Required Diagnostic:Identify the checkout request that returns HTTP 500 and inspect its response. -Required Diagnostic:Capture the complete browser Console error, including the source file and line number. -Required Diagnostic:Determine whether the failure occurs with one shipping method or every available shipping method. Implementation 1.Enable or inspect WordPress/WooCommerce logging without exposing errors to customers. 2.Reproduce the issue in a controlled session by selecting the shipping method once. 3.Record the exact PHP fatal error/exception and stack trace generated at that moment. 4.In browser Developer Tools, inspect the failed checkout AJAX/REST request and record its URL, HTTP status, request context, and response. 5.Record the complete JavaScript error and its source file/line. 6.Test whether the problem persists with the same shipping method after temporarily isolating nonessential custom checkout/shipping functionality in a staging environment. -No production code change should be made until these observations identify the failing component. Why This Works -The HTTP 500 is the strongest signal because it indicates that the server failed while processing the checkout operation. -The JavaScript error alone cannot establish that JavaScript is the root cause. It may simply be reacting to an unexpected 500 response. -The smallest reliable fix depends on the exact failing callback, exception, plugin, theme code, or integration identified by the server-side evidence. Security & Performance -Do not display PHP errors, stack traces, database errors, or credentials to customers. -Do not disable security controls, payment verification, shipping validation, or checkout protection as a troubleshooting shortcut. -Avoid adding debugging plugins or replacing existing checkout components unless the collected evidence requires them. Verification -Test 1:Select each relevant shipping method. -Expected:Shipping rates update without HTTP 500 responses. -Test 2:Complete checkout using a normal test order. -Expected:Checkout proceeds through payment without server or JavaScript errors. -Test 3:Check the browser Console and failed network requests. -Expected:No checkout-related JavaScript errors or unexpected 5xx responses. -Test 4:Review server logs after the successful test. -Expected:No new PHP fatal error or uncaught exception associated with checkout. If It Still Fails The next required evidence is: -Exact PHP fatal error/exception and stack trace from the server log. -Failing WooCommerce checkout AJAX/REST request and HTTP response. -Browser Console error with its full message and source file/line. -The selected shipping method when the failure occurs. -Any relevant custom checkout/shipping code or recent plugin/theme changes. Once those are available, the responsible component can be isolated and the smallest evidence-based fix can be specified without unnecessarily changing payment, shipping, caching, or checkout functionality.