NopCommerce 4.60.5 重启后 Nginx 返回 502 Bad Gateway 问题求助

各位大佬好，我现在被一个问题折腾整整7天了，网上能搜到的办法几乎都试了一遍，还是没解决，实在没办法来求助了！

我的环境是：NopCommerce 4.60.5 + Ubuntu 23 + Nginx反向代理.NET后端应用。网站平时正常运行，只有一些小问题在慢慢调试，但每次在后台修改设置后重启NopCommerce时，就会立刻出现502 Bad Gateway错误，查看Nginx的错误日志，显示的是“connection refused to upstream server”。更头疼的是，本地测试服务器和生产服务器环境完全一致，都出现了这个问题。

下面是我的Nginx配置文件内容：

server {
    # include snippets/snakeoil.conf;

    # Add index.php to the list if you are using PHP
    index index.html index.htm index.nginx-debian.html;

    server_name www.MYDOMAIN.ca MYDOMAIN.ca;

    location / {
        # First attempt to serve request as file, then
        # as directory, then fall back to displaying a 404.
        #try_files $uri $uri/ =404;

        proxy_pass         http://localhost:5000;
        add_header 'Content-Security-Policy' 'upgrade-insecure-requests';

        proxy_http_version    1.1;
        proxy_set_header      Upgrade $http_upgrade;
        proxy_set_header      Connection keep-alive;
        proxy_set_header      Host $host;
        #proxy_set_header      X-Real-IP $remote_addr;
        proxy_cache_bypass    $http_upgrade;
        #proxy_set_header      X-Forwarded-For $proxy_add_x_forwarded_for;
        #proxy_set_header      X-Forwarded-Proto $scheme;
        #proxy_set_header      X-Frame-Options SAMEORIGIN;
        #proxy_set_header      X-Forwarded-Host $host;
        #proxy_read_timeout    900;
    }

    listen [::]:443 ssl ipv6only=on; # managed by Certbot
    listen 443 ssl; # managed by Certbot
    server_name MYDOMAIN.ca www.MYDOMAIN.ca;
    ssl_certificate /etc/letsencrypt/live/supplysolution.ca/fullchain.pem; # managed by Certbot
    ssl_certificate_key /etc/letsencrypt/live/supplysolution.ca/privkey.pem; # managed by Certbot
    include /etc/letsencrypt/options-ssl-nginx.conf; # managed by Certbot
    ssl_dhparam /etc/letsencrypt/ssl-dhparams.pem; # managed by Certbot
}

server {
    if ($host = www.MYDOMAIN.ca) {
        return 301 https://$host$request_uri;
    } # managed by Certbot

    if ($host = MYDOMAIN.ca) {
        return 301 https://$host$request_uri;
    } # managed by Certbot

    listen 80;
    listen [::]:80;
    server_name MYDOMAIN.ca www.MYDOMAIN.ca;
    return 404; # managed by Certbot
}

真心希望各位能帮我找出问题所在，解决这个困扰我一周的麻烦！

备注：内容来源于stack exchange，提问作者tonysar