I created a ticket at WooCommerce last week about this and haven’t received a reply. Still getting the error, here’s my stack trace:
Error Details
=============
An error of type E_ERROR was caused in line 596 of the file /nas/content/live/thornebottomfa/wp-content/plugins/woocommerce-paypal-payments/modules/ppcp-subscription/src/SubscriptionModule.php. Error message: Uncaught Error: Call to undefined method WP_Post::get_meta() in /nas/content/live/thornebottomfa/wp-content/plugins/woocommerce-paypal-payments/modules/ppcp-subscription/src/SubscriptionModule.php:596
Stack trace:
#0 /nas/content/live/thornebottomfa/wp-includes/class-wp-hook.php(310): WooCommerce\PayPalCommerce\Subscription\SubscriptionModule->WooCommerce\PayPalCommerce\Subscription\{closure}(7284, Object(WP_Post))
#1 /nas/content/live/thornebottomfa/wp-includes/class-wp-hook.php(334): WP_Hook->apply_filters('', Array)
#2 /nas/content/live/thornebottomfa/wp-includes/plugin.php(517): WP_Hook->do_action(Array)
#3 /nas/content/live/thornebottomfa/wp-content/plugins/woocommerce-subscriptions/vendor/woocommerce/subscriptions-core/includes/admin/meta-boxes/class-wcs-meta-box-subscription-data.php(417): do_action('woocommerce_pro...', 7284, Object(WP_Post))
#4 /nas/content/live/thornebottomfa/wp-includes/class-wp-hook.php(310): WCS_Meta_Box_Subscription_Data::save(7284, Object(WP_Post))
#5 /nas/content/live/thornebottomfa/wp-includes/class-wp-hook.php(334): WP_Hook->apply_filters(NULL, Array)
#6 /nas/content/live/thornebottomfa/wp-includes/plugin.php(517): WP_Hook->do_action(Array)
#7 /nas/content/live/thornebottomfa/wp-content/plugins/woocommerce/includes/admin/class-wc-admin-meta-boxes.php(263): do_action('woocommerce_pro...', 7284, Object(WP_Post))
#8 /nas/content/live/thornebottomfa/wp-includes/class-wp-hook.php(312): WC_Admin_Meta_Boxes->save_meta_boxes(7284, Object(WP_Post))
#9 /nas/content/live/thornebottomfa/wp-includes/class-wp-hook.php(334): WP_Hook->apply_filters('', Array)
#10 /nas/content/live/thornebottomfa/wp-includes/plugin.php(517): WP_Hook->do_action(Array)
#11 /nas/content/live/thornebottomfa/wp-includes/post.php(4751): do_action('save_post', 7284, Object(WP_Post), true)
#12 /nas/content/live/thornebottomfa/wp-includes/post.php(4853): wp_insert_post(Array, false, true)
#13 /nas/content/live/thornebottomfa/wp-admin/includes/post.php(445): wp_update_post(Array)
#14 /nas/content/live/thornebottomfa/wp-admin/post.php(227): edit_post()
#15 {main}
thrown
Chris