Cannot save posts with Gutenberg

I have installed brand new WordPress and when I use Gutenberg, I cannot publish a new post. I receive a notification that the post is “saved”, then the title disappears and the post is not published or saved.
When I use classic editor, posts save just fine.
I guess it has something to do with my server and Gutenberg, but I cannot find exactly what.

So far I have tried the following:
– jumping to different PHP versions
– reinstalling WordPress a few times
– deleted all plugins and themes (but 1)
– making sure that .htaccess has nothing but default code
– saving permalinks to post name
– switched on debugging – no errors are logged

Here is my Health check info:

### wp-core ###

version: 5.9.3
site_language: en_GB
user_language: en_GB
timezone: Europe/London
permalink: /%postname%/
https_status: true
multisite: false
user_registration: 0
blog_public: 0
default_comment_status: open
environment_type: production
user_count: 1
dotorg_communication: true

### wp-paths-sizes ###

wordpress_path: /var/www/thedadlab/data/www/thedadlab.com
wordpress_size: 49.29 MB (51687264 bytes)
uploads_path: /var/www/thedadlab/data/www/thedadlab.com/wp-content/uploads
uploads_size: 0.00 B (0 bytes)
themes_path: /var/www/thedadlab/data/www/thedadlab.com/wp-content/themes
themes_size: 8.72 MB (9143438 bytes)
plugins_path: /var/www/thedadlab/data/www/thedadlab.com/wp-content/plugins
plugins_size: 28.00 B (28 bytes)
database_size: 9.22 MB (9666560 bytes)
total_size: 67.23 MB (70497290 bytes)

### wp-active-theme ###

name: Twenty Twenty-Two (twentytwentytwo)
version: 1.1
author: the WordPress team
author_website: https://en-gb.ww.wp.xz.cn/
parent_theme: none
theme_features: core-block-patterns, post-thumbnails, responsive-embeds, editor-styles, html5, automatic-feed-links, block-templates, widgets-block-editor, wp-block-styles, editor-style
theme_path: /var/www/thedadlab/data/www/thedadlab.com/wp-content/themes/twentytwentytwo
auto_update: Disabled

### wp-media ###

image_editor: WP_Image_Editor_GD
imagick_module_version: Not available
imagemagick_version: Not available
imagick_version: Not available
file_uploads: File uploads is turned off
post_max_size: 128M
upload_max_filesize: 100M
max_effective_size: 100 MB
max_file_uploads: 20
gd_version: bundled (2.1.0 compatible)
gd_formats: GIF, PNG, WebP, BMP, XPM
ghostscript_version: 8.70

### wp-server ###

server_architecture: Linux 2.6.32-642.11.1.el6.x86_64 x86_64
httpd_software: Apache/2.2.22 (@RELEASE@)
php_version: 7.4.10 64bit
php_sapi: cgi-fcgi
max_input_variables: 1000
time_limit: 30
memory_limit: 512M
max_input_time: 60
upload_max_filesize: 100M
php_post_max_size: 128M
curl_version: 7.19.7 NSS/3.27.1
suhosin: false
imagick_availability: false
pretty_permalinks: true
htaccess_extra_rules: true

### wp-database ###

extension: mysqli
server_version: 5.7.37
client_version: mysqlnd 7.4.10
max_allowed_packet: 4194304
max_connections: 151

### wp-constants ###

WP_HOME: https://thedadlab.com
WP_SITEURL: https://thedadlab.com
WP_CONTENT_DIR: /var/www/thedadlab/data/www/thedadlab.com/wp-content
WP_PLUGIN_DIR: /var/www/thedadlab/data/www/thedadlab.com/wp-content/plugins
WP_MEMORY_LIMIT: 40M
WP_MAX_MEMORY_LIMIT: 512M
WP_DEBUG: true
WP_DEBUG_DISPLAY: true
WP_DEBUG_LOG: true
SCRIPT_DEBUG: false
WP_CACHE: false
CONCATENATE_SCRIPTS: undefined
COMPRESS_SCRIPTS: undefined
COMPRESS_CSS: undefined
WP_ENVIRONMENT_TYPE: Undefined
DB_CHARSET: utf8mb4
DB_COLLATE: undefined

### wp-filesystem ###

wordpress: writable
wp-content: writable
uploads: writable
plugins: writable
themes: writable

The page I need help with: [log in to see the link]