guavadesign

Thanks for the reply, Darla. The issue has since improved, although the only thing I did disable was a drop-in Object Cache plugin which used the PHP OPCache extension as an Object Cache storage mechanism. Maybe this was conflicting things.

I also re-installed the WooCommerce Payments plugin and asked my client to re-link it to their WordPress account, and things do seem to have calmed down. But there was a good 2-3 days where they were unable to use WooCommerce Payments at all on the website due to the performance problems.

There were some entries in the fatal log from over the past few days when the issue was happening:

2023-08-01T20:38:34+00:00 CRITICAL Uncaught TypeError: Argument 1 passed to WC_Payments_Utils::encrypt_client_secret() must be of the type string, null given, called in /path/to/wp/public_html/wp-content/plugins/woocommerce-payments/includes/payment-methods/class-upe-split-payment-gateway.php on line 247 and defined in /path/to/wp/public_html/wp-content/plugins/woocommerce-payments/includes/class-wc-payments-utils.php:867
Stack trace:
#0 /path/to/wp/public_html/wp-content/plugins/woocommerce-payments/includes/payment-methods/class-upe-split-payment-gateway.php(247): WC_Payments_Utils::encrypt_client_secret(NULL, 'pi_...')
#1 /path/to/wp/public_html/wp-includes/class-wp-hook.php(308): WCPay\Payment_Methods\UPE_Split_Payment_Gateway->create_payment_intent_ajax('')
#2 /path/to/wp/public_html/wp-includes/class-wp-hook.php(332): WP_Hook->apply_filters('', Array)
#3 /path/to/wp/public_html/wp-includes/plugin.php(517): WP_Hook->do_action(Array)
#4 /path/to/wp/pub in /path/to/wp/public_html/wp-content/plugins/woocommerce-payments/includes/class-wc-payments-utils.php on line 867

2023-08-01T20:41:11+00:00 CRITICAL Uncaught TypeError: Argument 1 passed to WC_Payments_Utils::encrypt_client_secret() must be of the type string, null given, called in /path/to/wp/public_html/wp-content/plugins/woocommerce-payments/includes/payment-methods/class-upe-split-payment-gateway.php on line 247 and defined in /path/to/wp/public_html/wp-content/plugins/woocommerce-payments/includes/class-wc-payments-utils.php:867
Stack trace:
#0 /path/to/wp/public_html/wp-content/plugins/woocommerce-payments/includes/payment-methods/class-upe-split-payment-gateway.php(247): WC_Payments_Utils::encrypt_client_secret(NULL, 'pi_...')
#1 /path/to/wp/public_html/wp-includes/class-wp-hook.php(308): WCPay\Payment_Methods\UPE_Split_Payment_Gateway->create_payment_intent_ajax('')
#2 /path/to/wp/public_html/wp-includes/class-wp-hook.php(332): WP_Hook->apply_filters('', Array)
#3 /path/to/wp/public_html/wp-includes/plugin.php(517): WP_Hook->do_action(Array)
#4 /path/to/wp/pub in /path/to/wp/public_html/wp-content/plugins/woocommerce-payments/includes/class-wc-payments-utils.php on line 867

2023-08-01T20:42:37+00:00 CRITICAL Uncaught TypeError: Argument 1 passed to WC_Payments_Utils::encrypt_client_secret() must be of the type string, null given, called in /path/to/wp/public_html/wp-content/plugins/woocommerce-payments/includes/payment-methods/class-upe-split-payment-gateway.php on line 247 and defined in /path/to/wp/public_html/wp-content/plugins/woocommerce-payments/includes/class-wc-payments-utils.php:867
Stack trace:
#0 /path/to/wp/public_html/wp-content/plugins/woocommerce-payments/includes/payment-methods/class-upe-split-payment-gateway.php(247): WC_Payments_Utils::encrypt_client_secret(NULL, 'pi_...')
#1 /path/to/wp/public_html/wp-includes/class-wp-hook.php(308): WCPay\Payment_Methods\UPE_Split_Payment_Gateway->create_payment_intent_ajax('')
#2 /path/to/wp/public_html/wp-includes/class-wp-hook.php(332): WP_Hook->apply_filters('', Array)
#3 /path/to/wp/public_html/wp-includes/plugin.php(517): WP_Hook->do_action(Array)
#4 /path/to/wp/pub in /path/to/wp/public_html/wp-content/plugins/woocommerce-payments/includes/class-wc-payments-utils.php on line 867

2023-08-01T23:02:03+00:00 CRITICAL require(): Failed opening required '/path/to/wp/public_html/wp-content/plugins/woocommerce-payments/dist/blocks-checkout.asset.php' (include_path='.:/opt/alt/php74/usr/share/pear') in /path/to/wp/public_html/wp-content/plugins/woocommerce-payments/includes/class-wc-payments.php on line 1077

2023-08-01T23:02:15+00:00 CRITICAL require(): Failed opening required '/path/to/wp/public_html/wp-content/plugins/woocommerce/src/Internal/Admin/Schedulers/CustomersScheduler.php' (include_path='.:/opt/alt/php74/usr/share/pear') in /path/to/wp/public_html/wp-content/plugins/woocommerce-payments/vendor/jetpack-autoloader/class-php-autoloader.php on line 90

2023-08-01T23:02:15+00:00 CRITICAL require(): Failed opening required '/path/to/wp/public_html/wp-content/plugins/woocommerce/src/Internal/Admin/Schedulers/CustomersScheduler.php' (include_path='.:/opt/alt/php74/usr/share/pear') in /path/to/wp/public_html/wp-content/plugins/woocommerce-payments/vendor/jetpack-autoloader/class-php-autoloader.php on line 90

2023-08-01T23:02:16+00:00 CRITICAL require(): Failed opening required '/path/to/wp/public_html/wp-content/plugins/woocommerce/src/Admin/ReportsSync.php' (include_path='.:/opt/alt/php74/usr/share/pear') in /path/to/wp/public_html/wp-content/plugins/woocommerce-payments/vendor/jetpack-autoloader/class-php-autoloader.php on line 90

2023-08-01T23:02:37+00:00 CRITICAL require(): Failed opening required '/path/to/wp/public_html/wp-content/plugins/woocommerce/packages/woocommerce-blocks/src/BlockTypes/ProductTopRated.php' (include_path='.:/opt/alt/php74/usr/share/pear') in /path/to/wp/public_html/wp-content/plugins/woocommerce-payments/vendor/jetpack-autoloader/class-php-autoloader.php on line 90

2023-08-01T23:02:37+00:00 CRITICAL require(): Failed opening required '/path/to/wp/public_html/wp-content/plugins/woocommerce/packages/woocommerce-blocks/src/BlockTypes/ProductTopRated.php' (include_path='.:/opt/alt/php74/usr/share/pear') in /path/to/wp/public_html/wp-content/plugins/woocommerce-payments/vendor/jetpack-autoloader/class-php-autoloader.php on line 90

2023-08-01T23:02:37+00:00 CRITICAL require(): Failed opening required '/path/to/wp/public_html/wp-content/plugins/woocommerce/packages/woocommerce-blocks/src/BlockTypes/ProductTopRated.php' (include_path='.:/opt/alt/php74/usr/share/pear') in /path/to/wp/public_html/wp-content/plugins/woocommerce-payments/vendor/jetpack-autoloader/class-php-autoloader.php on line 90

2023-08-04T12:06:43+00:00 CRITICAL require(): Failed opening required '/path/to/wp/public_html/wp-content/plugins/woocommerce-payments/vendor/automattic/jetpack-connection/src/class-rest-connector.php' (include_path='.:/opt/alt/php74/usr/share/pear') in /path/to/wp/public_html/wp-content/plugins/woocommerce-payments/vendor/jetpack-autoloader/class-php-autoloader.php on line 90

2023-08-04T12:06:48+00:00 CRITICAL require(): Failed opening required '/path/to/wp/public_html/wp-content/plugins/woocommerce-payments/vendor/automattic/jetpack-connection/src/class-rest-connector.php' (include_path='.:/opt/alt/php74/usr/share/pear') in /path/to/wp/public_html/wp-content/plugins/woocommerce-payments/vendor/jetpack-autoloader/class-php-autoloader.php on line 90

Just FYI, we’re not using JetPack on this website (but AFAIK it’s not a requirement).

Looking into all of the above, I’m thinking that perhaps the website might have lost its connection with WordPress and therefore was timing out trying to talk to WooCommerce Payments? Re-linking it maybe sorted it.