Aktualisierung fehlgeschlagen. Die Antwort ist keine gültige JSON-Antwort.

Hallo,
ich bekomme seit heute (habe heute meine Website auf dem Server meines Hosters IONOS übertragen) beim Ändern von Text die Fehlermeldung:
Aktualisierung fehlgeschlagen. Die Antwort ist keine gültige JSON-Antwort.

Könnt ihr mir weiterhelfen?
Dankeschön!

Hier kommt der Bericht:

### wp-core ###

version: 5.5.1
site_language: de_DE
user_language: de_DE
permalink: /%postname%/
https_status: true
user_registration: 0
default_comment_status: open
multisite: false
user_count: 1
dotorg_communication: true

### wp-paths-sizes ###

wordpress_path: /homepages/31/d831227508/htdocs
wordpress_size: 48,92 MB (51294731 bytes)
uploads_path: /homepages/31/d831227508/htdocs/wp-content/uploads
uploads_size: 8,60 MB (9019553 bytes)
themes_path: /homepages/31/d831227508/htdocs/wp-content/themes
themes_size: 17,02 MB (17846418 bytes)
plugins_path: /homepages/31/d831227508/htdocs/wp-content/plugins
plugins_size: 43,40 MB (45505263 bytes)
database_size: 3,47 MB (3637248 bytes)
total_size: 121,41 MB (127303213 bytes)

### wp-active-theme ###

name: Twenty Seventeen (twentyseventeen)
version: 2.4
author: WordPress-Team
author_website: https://de.wordpress.org/
parent_theme: none
theme_features: core-block-patterns, automatic-feed-links, title-tag, post-thumbnails, menus, html5, post-formats, custom-logo, customize-selective-refresh-widgets, editor-style, editor-styles, wp-block-styles, responsive-embeds, starter-content, custom-header, widgets
theme_path: /homepages/31/d831227508/htdocs/wp-content/themes/twentyseventeen

### wp-themes-inactive (3) ###

OceanWP: version: 1.9.0, author: Nick
Twenty Nineteen: version: 1.7, author: WordPress-Team
Twenty Twenty: version: 1.5, author: WordPress-Team

### wp-plugins-active (4) ###

Contact Form 7: version: 5.2.2, author: Takayuki Miyoshi
Health Check & Troubleshooting: version: 1.4.5, author: The WordPress.org community
Maintenance: version: 3.97, author: WebFactory Ltd
Yoast SEO: version: 15.1.1, author: Team Yoast

### wp-plugins-inactive (6) ###

Akismet Anti-Spam: version: 4.1.6, author: Automattic
Classic Editor: version: 1.6, author: WordPress Contributors
Elementor: version: 3.0.11, author: Elementor.com
Enable jQuery Migrate Helper: version: 1.1.0, author: The WordPress Team
Gutenberg: version: 9.1.1, author: Gutenberg Team
Hello Dolly: version: 1.7.2, author: Matt Mullenweg

### wp-media ###

image_editor: WP_Image_Editor_GD
imagick_module_version: Nicht verfügbar
imagemagick_version: Nicht verfügbar
gd_version: 2.2.5
ghostscript_version: 9.27

### wp-server ###

server_architecture: Linux 4.4.232-icpu-051 x86_64
httpd_software: Apache
php_version: 7.4.10 64bit
php_sapi: cgi-fcgi
max_input_variables: 5000
time_limit: 50000
memory_limit: -1
max_input_time: -1
upload_max_size: 64M
php_post_max_size: 64M
curl_version: 7.64.0 OpenSSL/1.1.1d
suhosin: false
imagick_availability: false
server-headers: 
	content-type: text/html; charset=UTF-8
	date: Sun, 18 Oct 2020 11:49:40 GMT
	server: Apache
	x-powered-by: PHP/7.4.10
	expires: Wed, 11 Jan 1984 05:00:00 GMT
	cache-control: no-cache, must-revalidate, max-age=0
	link: <https://kraftvision.de/wp-json/>; rel="https://api.w.org/", <https://kraftvision.de/wp-json/wp/v2/pages/52>; rel="alternate"; type="application/json", <https://kraftvision.de/>; rel=shortlink
	content-encoding: gzip
htaccess_extra_rules: true

### wp-database ###

extension: mysqli
server_version: 5.7.30-log
client_version: mysqlnd 7.4.10

### wp-constants ###

WP_HOME: undefined
WP_SITEURL: undefined
WP_CONTENT_DIR: /homepages/31/d831227508/htdocs/wp-content
WP_PLUGIN_DIR: /homepages/31/d831227508/htdocs/wp-content/plugins
WP_MAX_MEMORY_LIMIT: -1
WP_DEBUG: false
WP_DEBUG_DISPLAY: true
WP_DEBUG_LOG: false
SCRIPT_DEBUG: false
WP_CACHE: false
CONCATENATE_SCRIPTS: undefined
COMPRESS_SCRIPTS: undefined
COMPRESS_CSS: undefined
WP_LOCAL_DEV: undefined

### wp-filesystem ###

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