How to solve ERR_INVALID_REDIRECT for an HTTPS Wordpress website on Apache behind Nginx and varnish? [closed]

My website home page returns "ERR_INVALID_REDIRECT". All the other pages of the website are fine. It just returns this issue for the Homepage (meaning: https://www.mywebsiteurl.com/).

The reason is that Wordpress decides to redirect to "https:///" (cf. screenshot below: X-redirect-by: Wordpress)

I have already:

• Cleared my browser cache
• Restarted Nginx, Varnish and Apache
• Deactivated the plugins from wordpress
• in my wp-config.php file the WP_HOME and WP_SITEURL are set properly.

I did just upgraded to Wordpress: 5.6.1 and also updated my Theme yesterday. There was no problem before the upgrade. So the problem is certainly coming from one of these actions.

My question is, What else should I check?What are the next actions that I could take the figure out where the problem comes from? Any advanced debugging I could do somehow?

Thanks a lot.

UPDATE #1

Mywebsite.conf

<VirtualHost *:8080>   ServerName www.mywebsite.com   DocumentRoot /var/www/wordpress/   LogFormat "%{X-Forwarded-For}i %l %u %t \"%r\" %>s %b \"%{User-agent}i\"" varnishcombined   ErrorLog /var/log/apache2/wordpress/mywebsite-error.log   CustomLog /var/log/apache2/wordpress/mywebsite-access.log varnishcombined</VirtualHost>

wordpress.conf

<Directory /var/www/wordpress/>     Options Indexes FollowSymLinks     AllowOverride All     Require all granted</Directory><VirtualHost *:80>     ServerName 139.162.xx.xx #I masked the IP here     #Redirect permanent / http://www.mywebsite.com/     ServerAdmin webmaster@localhost     DocumentRoot /var/www/wordpress/     ErrorLog /var/log/apache2/wordpress/error.log     CustomLog /var/log/apache2/wordpress/access.log combined<files xmlrpc.php>       order allow,deny       deny from all </files></VirtualHost>

The last virtual host from wordpress.com should not be taken in to account because Apache just listens on port 8080.Nginx, my front webserver listens on port 80 and 443.

UPDATE #2

mywebsite.conf (Nginx conf)

server {  listen 443;  server_name www.mywebsite.com;  port_in_redirect off;  ssl on;  ssl_certificate /etc/ssl/private/mywebsite.com.chained.crt;  ssl_certificate_key /etc/ssl/private/mywebsite_com_key.txt;  ssl_protocols TLSv1 TLSv1.1 TLSv1.2;  ssl_ciphers ECDH+AESGCM:DH+AESGCM:ECDH+AES256:DH+AES256:ECDH+AES128:DH+AES:ECDH+3DES:DH+3DES:RSA+AESGCM:RSA+AES:RSA+3DES:!aNULL:!MD5:!dSS;  ssl_prefer_server_ciphers   on;  ssl_session_cache   shared:SSL:20m;  ssl_session_timeout 60m;  add_header Strict-Transport-Security "max-age=31536000";  add_header X-Content-Type-Options nosniff;  location / {     proxy_pass            http://127.0.0.1:6081;     proxy_read_timeout    90;     proxy_redirect        off;     proxy_set_header      X-Real-IP $remote_addr;     proxy_set_header      X-Forwarded-For $proxy_add_x_forwarded_for;     proxy_set_header      X-Forwarded-Proto https;     proxy_set_header      X-Forwarded-Port 443;     proxy_set_header      Host $host;     proxy_set_header      X-Forwarded-Host $http_host;     proxy_set_header      HTTPS "on";   }}server {   listen 443 ssl;   server_name mywebsite.com;   return 301 https://www.mywebsite.com$request_uri;}server {   listen 80 default_server;   server_name _;   return 301 https://$host$request_uri;}

UPDATE #3

 #curl -v -H 'Host: www.mywebsite.com' http://127.0.0.1:8080/ * Expire in 0 ms for 6 (transfer 0x56356f708f50) *   Trying 127.0.0.1... * TCP_NODELAY set * Expire in 200 ms for 4 (transfer 0x56356f708f50) * Connected to 127.0.0.1 (127.0.0.1) port 8080 (#0)> GET / HTTP/1.1> Host: www.mywebsite.com> User-Agent: curl/7.64.0> Accept: */*> < HTTP/1.1 301 Moved Permanently< Date: Wed, 24 Feb 2021 14:32:06 GMT< Server: Apache/2.4.38 (Debian)< X-Redirect-By: WordPress< Location: https://www.mywebsite.com/< Content-Length: 0< Content-Type: text/html; charset=UTF-8<  * Connection #0 to host 127.0.0.1 left intact