upstream timed out (110: Connection timed out) while reading response header from upstream: "fastcgi://unix:/run/php/php7.3-fpm.sock"

I just migrated from Google Cloud to DigitalOcean yesterday. Now I experience theese weird php-fpm errors in my /var/log/nginx/error.log:

2019/09/25 08:09:41 [error] 4339#4339: *9138 upstream timed out (110: Connection timed out) while reading response header from upstream, client: 109.59.211.232, server: SOME_IP, request: "POST /wp-admin/post.php HTTP/1.1", upstream: "fastcgi://unix:/run/php/php7.3-fpm.sock", host: "mywebsite.com", referrer: "https://mywebsite.com/wp-admin/post-new.php?post_type=shop_coupon&wp-post-new-reload=true&wp-post-new-reload=true"
2019/09/25 08:10:28 [error] 4339#4339: *9169 upstream timed out (110: Connection timed out) while reading response header from upstream, client: 109.59.211.232, server: SOME_IP, request: "GET /da/produkt-kategori/oereringe/ HTTP/1.1", upstream: "fastcgi://unix:/run/php/php7.3-fpm.sock", host: "mywebsite.com", referrer: "https://mywebsite.com/product-category/earrings/"

This is my nginx configuration:

server {

    # SSL configuration
    #
    # listen 443 ssl default_server;
    # listen [::]:443 ssl default_server;
    #
    # Note: You should disable gzip for SSL traffic.
    # See: https://bugs.debian.org/773332
    #
    # Read up on ssl_ciphers to ensure a secure configuration.
    # See: https://bugs.debian.org/765782
    #
    # Self signed certs generated by the ssl-cert package
    # Don't use them in a production server!
    #
    # include snippets/snakeoil.conf;

    root /var/www/html/current;

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

    server_name MYIP mywebsite.com www.mywebsite.com;

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

    # pass the PHP scripts to FastCGI server listening on 127.0.0.1:9000
    #
    location ~ \.php$ {
        include snippets/fastcgi-php.conf;

        # see https://gist.github.com/magnetikonline/11312172#determine-fastcgi-response-sizes
        fastcgi_buffers 8 16k;
        fastcgi_buffer_size 32k;

    #
    #   # With php7.0-cgi alone:
    #   fastcgi_pass 127.0.0.1:9000;
    #   # With php7.0-fpm:
        fastcgi_pass unix:/run/php/php7.3-fpm.sock;
    }

    # deny access to .htaccess files, if Apache's document root
    # concurs with nginx's one
    #
    location ~ /\.ht {
       deny all;
    }


    #WordPress specific

        location = /favicon.ico {
                log_not_found off;
                access_log off;
        }

        location = /robots.txt {
                allow all;
                log_not_found off;
                access_log off;
        }

        location ~* \.(js|css|png|jpg|jpeg|gif|ico)$ {
                expires max;
                log_not_found off;
        }

        #W3 TOTAL CACHE CHECK
        set $cache_uri $request_uri;

        # POST requests and urls with a query string should always go to PHP
        if ($request_method = POST) {
                set $cache_uri 'null cache';
        }
        if ($query_string != "") {
                set $cache_uri 'null cache';
        }

        # Don't cache uris containing the following segments
        if ($request_uri ~* "(/wp-admin/|/xmlrpc.php|/wp-(app|cron|login|register|mail).php|wp-.*.php|/feed/|index.php|wp-comments-popup.php|wp-links-opml.php|wp-locations.php|sitemap(_index)?.xml|[a-z0-9_-]+-sitemap([0-9]+)?.xml)") {
                set $cache_uri 'null cache';
        }

        # Don't use the cache for logged in users or recent commenters
        if ($http_cookie ~* "comment_author|wordpress_[a-f0-9]+|wp-postpass|wordpress_logged_in") {
                set $cache_uri 'null cache';
        }
        #ADD mobile rules from WP SUPER CACHE section above
        #APPEND A CODE BLOCK FROM BELOW..

        # Use cached or actual file if they exists, otherwise pass request to WordPress
        location / {
                try_files /wp-content/w3tc/pgcache/$cache_uri/_index.html $uri $uri/ /index.php?$args ;
        }


    listen 443 ssl; # managed by Certbot
    ssl_certificate /etc/letsencrypt/live/mywebsite.com/fullchain.pem; # managed by Certbot
    ssl_certificate_key /etc/letsencrypt/live/mywebsite.com/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


}


# Virtual Host configuration for example.com
#
# You can move that to a different file under sites-available/ and symlink that
# to sites-enabled/ to enable it.
#
#server {
#   listen 80;
#   listen [::]:80;
#
#   server_name example.com;
#
#   root /var/www/example.com;
#   index index.html;
#
#   location / {
#       try_files $uri $uri/ =404;
#   }
#}

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


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



    server_name MYIP mywebsite.com www.mywebsite.com;
    listen 80;
    return 404; # managed by Certbot




}

What could possibly be wrong?