RSS Feed Problem

Hi, I currently updatet to WordPress version 4.7. Now i wanted to add an RSS Feed to my side. Every Plugin i tried gives me a white page when trying to preview or publish the page.
I used WP RSS and Feedzy RSS Feeds Version 2.8.1.
There is no errors while debugging and the preview page and published page seem to not have any content in the body tag.

Can anyone help?

Here is all the information to plugins, php version and so on in case you will need it

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### WordPress Environment ###

Home URL: https://www.netz-mitteldeutschland.de
Site URL: https://www.netz-mitteldeutschland.de
WC Version: 2.6.9
Log Directory Writable: ?
WP Version: 4.7
WP Multisite: –
WP Memory Limit: 256 MB
WP Debug Mode: ?
WP Cron: ?
Language: de_DE

### Server Environment ###

Server Info: Apache
PHP Version: 5.6.29
PHP Post Max Size: 50 MB
PHP Time Limit: 0
PHP Max Input Vars: 5000
cURL Version: 7.38.0
OpenSSL/1.0.1t

SUHOSIN Installed: –
MySQL Version: ? 5.5.53 – Wir empfehlen mindestens MySQL-Version 5.6. Siehe: WordPress-Anforderungen
Max Upload Size: 50 MB
Default Timezone is UTC: ?
fsockopen/cURL: ?
SoapClient: ?
DOMDocument: ?
GZip: ?
Multibyte String: ?
Remote Post: ?
Remote Get: ?

### Database ###

WC Database Version: 2.6.9
:
woocommerce_sessions: ?
woocommerce_api_keys: ?
woocommerce_attribute_taxonomies: ?
woocommerce_downloadable_product_permissions: ?
woocommerce_order_items: ?
woocommerce_order_itemmeta: ?
woocommerce_tax_rates: ?
woocommerce_tax_rate_locations: ?
woocommerce_shipping_zones: ?
woocommerce_shipping_zone_locations: ?
woocommerce_shipping_zone_methods: ?
woocommerce_payment_tokens: ?
woocommerce_payment_tokenmeta: ?
MaxMind GeoIP Database: ?

### Active Plugins (45) ###

AdRotate: von Arnan de Gans – 3.16.3
Advanced Woo Search: von ILLID – 1.09
Basic Comment Quicktags: von Mika “Ipstenu” Epstein – 3.3.1
Bee Pricing Table: von aumsrini – 1.0.0
Better Search Replace: von Delicious Brains – 1.3
Bowe Codes: von imath – 2.1
BP Simple Private: von shanebp – 1.3
BP WC Vendors – übersetzung: von Rebecca Blischke – 1.0.8
rtMedia for WordPress, BuddyPress and bbPress: von rtCamp – 4.2
BuddyPress Profile Shortcodes: von Bento4Extend – 1.1
BuddyPress: von Die BuddyPress Community – 2.7.4
Business Directory Plugin: von D. Rodenbaugh – 4.1.5
Closify Maestro: von Abdulrhman Elbuni – 1.9.2.3
Kommentar-Anhang: von latorante – 1.5.7
Contact Form 7 Honeypot: von Nocean – 1.10
Contact Form 7: von Takayuki Miyoshi – 4.6
The Events Calendar PRO: von Modern Tribe
Inc. – 4.3.3

FEEDZY RSS Feeds: von Themeisle – 2.8.1
Flamingo: von Takayuki Miyoshi – 1.5
WPBakery Visual Composer: von Michael M – WPBakery.com – 4.12.1
Loco Translate: von Tim Whitlock – 2.0.11
Login Widget With Shortcode: von aviplugins.com – 5.5.5
Post Views Counter: von dFactory – 1.2.4
Really Simple SSL: von Rogier Lankhorst – 2.4.3
s2Member Framework: von s2Member / WebSharks
Inc. – 161129

Suchen & Ersetzen: von Inpsyde GmbH – 3.1.0
Sidebar Login: von Mike Jolley – 2.7.3
BuddyPress Simple Terms And Conditions: von Florian Mai – 1.3
Socialize Plugin: von GhostPool – 3.1.2
TablePress: von Tobias B?thge – 1.7
The Events Calendar: Community Events: von Modern Tribe
Inc. – 4.3.1

The Events Calendar: von Modern Tribe
Inc. – 4.3.5

Theia Sticky Sidebar: von WeCodePixels – 1.6.3
TI Wishlist – CUSTOMIZED: von Rebecca Blischke – 1.0.0
User Role Editor: von Vladimir Garagulya – 4.31
User Roles and Capabilities: von mahabub – 1.2.1
WC Vendors Pro: von WC Vendors – 1.3.8
WC Vendors: von WC Vendors – 1.9.7
WooCommerce Extra Product Sorting Options: von SkyVerge – 2.5.0
WooCommerce: von WooThemes – 2.6.9
Yoast SEO: von Team Yoast – 4.0
WP Job Manager: von Automattic
Inc. – 1.25.2

WP Maintenance Mode: von Designmodo – 2.0.9
WP Migrate DB: von Delicious Brains – 0.9.2
WP-ReportPost: von Rajeevan – 1.2.4

### Settings ###

Force SSL: ?
Currency: EUR (€)
Currency Position: right_space
Thousand Separator: .
Decimal Separator: ,
Number of Decimals: 2

### API ###

API Enabled: ?

### WC Pages ###

Shop-Basis: #3820 – /marktplatz/
Warenkorb: #3547 – /cart/
Kasse: #3548 – /checkout/
Mein Konto: #3549 – /my-account/

### Taxonomies ###

Product Types: external (external)
grouped (grouped)
simple (simple)
variable (variable)

### Theme ###

Name: Socialize Child
Version: 1.0
Author URL: https://www.ghostpool.com
Child Theme: ?
Parent Theme Name: Socialize
Parent Theme Version: 2.19.1
Parent Theme Author URL: https://www.ghostpool.com
WooCommerce Support: ?

### Templates ###

Overrides: –

### WC Vendors Pro ###

Theme Compatability: –
Pro Dashboard Page: – #4516
Feedback form page: – #4517
Vendor Shop Permalink: – vendors/