Error reconnecting to the database when adding an image to a post

Hi,

I’m facing issues with my site.
It all started with slowness in the site and chasing timeout. After optimizing the DB it currently point to the Avia Builder.

The easiest way to trigger the error is create a new blog post and try to add an image to it with the builder. This triggers a:

Error reconnecting to the database
This means that we lost contact with the database server at localhost. This could mean your host’s database server is down.

This is what I find in the debug.log

[07-Nov-2020 15:18:50 UTC] PHP Notice: QM_DB was called <strong>incorrectly</strong>. QM_DB must set a database connection for use with escaping. Please see <a href="https://wordpress.org/support/article/debugging-in-wordpress/">Debugging in WordPress</a> for more information. (This message was added in version 3.6.0.) in /home/wp/disk/wordpress/wp-includes/functions.php on line 5229
[07-Nov-2020 15:18:50 UTC] PHP Notice: QM_DB was called <strong>incorrectly</strong>. QM_DB must set a database connection for use with escaping. Please see <a href="https://wordpress.org/support/article/debugging-in-wordpress/">Debugging in WordPress</a> for more information. (This message was added in version 3.6.0.) in /home/wp/disk/wordpress/wp-includes/functions.php on line 5229
[07-Nov-2020 15:18:48 UTC] PHP Warning: mysqli_real_connect(): (HY000/2002): Connection refused in /home/wp/disk/wordpress/wp-includes/wp-db.php on line 1635
[07-Nov-2020 15:18:48 UTC] PHP Warning: mysqli_real_connect(): (HY000/2002): Connection refused in /home/wp/disk/wordpress/wp-includes/wp-db.php on line 1635
[07-Nov-2020 15:18:44 UTC] PHP Warning: mysqli_real_connect(): (HY000/2002): Connection refused in /home/wp/disk/wordpress/wp-includes/wp-db.php on line 1635

When using wp blocks or changing the theme to woocommerce store front, the issue is not triggered.
I just manually upgraded to enfold 4.7.6.4

The hosting package has more than enough resources to work. I actually doubled it to be able to troubleshoot.