critical error

sometimes, website going to the critical error when trying send email to the customer.
for example if we try cancel order.
please check on your side what maybe a reason.

#2 /var/www/killapods_eu_usr/data/www/killapods.eu/wp-includes/plugin.php(205): WP_Hook->apply_filters(Array, Array)
#3 /var/www/killapods_eu_usr/data/www/killapods.eu/wp-content/plugins/woocommerce/includes/class-wc-payment-gateways.php(163): apply_filters(‘woocommerce_ava…’, Array)
#4 /var/www/killapods_eu_usr/data/www/killapods.eu/wp-content/plugins/woocommerce/src/Admin/Features/Onboarding” while reading response header from upstream, client: 83.69.236.107, server: killapods.eu, request: “GET /wp-json/wc-admin/onboarding/tasks?_locale=user HTTP/2.0”, upstream: “fastcgi://unix:/var/run/killapods.eu.sock:”, host: “killapods.eu”, referrer: “https://killapods.eu/wp-admin/edit.php?post_type=shop_order”
2023/04/19 18:30:09 [error] 2986149#2986149: *192684 FastCGI sent in stderr: “PHP message: PHP Fatal error: Uncaught Error: Call to a member function get_cart() on null in /var/www/killapods_eu_usr/data/www/killapods.eu/wp-content/plugins/wc-restrict-payment-method/includes/class-wcrpm-frontend.php:249
Stack trace:
#0 /var/www/killapods_eu_usr/data/www/killapods.eu/wp-content/plugins/wc-restrict-payment-method/includes/class-wcrpm-frontend.php(54): WCRPM_Restrict_Payment_Method_Frontend->wcrpm_check_products_in_cart()
#1 /var/www/killapods_eu_usr/data/www/killapods.eu/wp-includes/class-wp-hook.php(308): WCRPM_Restrict_Payment_Method_Frontend->wcrpm_available_payment_gateways(Array)
#2 /var/www/killapods_eu_usr/data/www/killapods.eu/wp-includes/plugin.php(205): WP_Hook->apply_filters(Array, Array)
#3 /var/www/killapods_eu_usr/data/www/killapods.eu/wp-content/plugins/woocommerce/includes/class-wc-payment-gateways.php(163): apply_filters(‘woocommerce_ava…’, Array)
#4 /var/www/killapods_eu_usr/data/www/killapods.eu/wp-content/plugins/woocommerce/src/Admin/Features/Onboarding” while reading response header from upstream, client: 83.69.236.107, server: killapods.eu, request: “GET /wp-json/wc-admin/onboarding/tasks?_locale=user HTTP/2.0”, upstream: “fastcgi://unix:/var/run/killapods.eu.sock:”, host: “killapods.eu”, referrer: “https://killapods.eu/wp-admin/edit.php?s=turunen.tomi%40live.fi&post_status=all&post_type=shop_order&action=-1&m=0&wcu_coupons&_customer_user&paged=1&action2=-1”
2023/04/19 18:34:08 [error] 2986149#2986149: *194018 directory index of “/var/www/killapods_eu_usr/data/www/killapods.eu//wp-admin/css/” is forbidden, client: 20.84.65.224, server: killapods.eu, request: “GET /wp-admin/css/ HTTP/1.1”, host: “killapods.eu”, referrer: “binance.com”
2023/04/19 18:34:19 [error] 2986149#2986149: *193958 FastCGI sent in stderr: “PHP message: PHP Fatal error: Uncaught Error: Call to a member function get_cart() on null in /var/www/killapods_eu_usr/data/www/killapods.eu/wp-content/plugins/wc-restrict-payment-method/includes/class-wcrpm-frontend.php:249
Stack trace:
#0 /var/www/killapods_eu_usr/data/www/killapods.eu/wp-content/plugins/wc-restrict-payment-method/includes/class-wcrpm-frontend.php(54): WCRPM_Restrict_Payment_Method_Frontend->wcrpm_check_products_in_cart()
#1 /var/www/killapods_eu_usr/data/www/killapods.eu/wp-includes/class-wp-hook.php(308): WCRPM_Restrict_Payment_Method_Frontend->wcrpm_available_payment_gateways(Array)
#2 /var/www/killapods_eu_usr/data/www/killapods.eu/wp-includes/plugin.php(205): WP_Hook->apply_filters(Array, Array)
#3 /var/www/killapods_eu_usr/data/www/killapods.eu/wp-content/plugins/woocommerce/includes/class-wc-payment-gateways.php(163): apply_filters(‘woocommerce_ava…’, Array)
#4 /var/www/killapods_eu_usr/data/www/killapods.eu/wp-content/plugins/woocommerce/src/Admin/Features/Onboarding” while reading response header from upstream, client: 78.56.76.85, server: killapods.eu, request: “GET /wp-json/wc-admin/onboarding/tasks?_locale=user HTTP/2.0”, upstream: “fastcgi://unix:/var/run/killapods.eu.sock:”, host: “killapods.eu”, referrer: “https://killapods.eu/wp-admin/edit.php?post_type=shop_order”