fatal error after updating the CF7 to v. 5.9.3

Where can we see the website in question?

PHP Fatal error: Allowed memory size of 536870912 bytes exhausted (tried to allocate 262144 bytes) in /var/www/html/site/wp-content/plugins/contact-form-7/includes/capabilities.php on line 17″

downgrade to 5.9.2 fixes the problem

The website in question: https://stb-steuerberater.de/en/contact-tax-advisor-in-mannheim/

What other plugins and theme do you use on the site?

@Takayuki Miyoshi Here’s the list of active plugins I’m using on the website: https://ibb.co/YT0vSwP
The theme is Finvizor Version: 1.0.0 (is discontinued and has never been upgraded any further than 1.0)

@gr3p: to downgrade to 5.9.2 will I need to remove the current version and re-create the existing forms?

Try switching to the default theme, deactivating all plugins excluding Contact Form 7, Akismet Anti-spam, Wordfence Security and Yoast SEO, and clearing all cache data.

Why you are advised to deactivate plugins and switch to the default theme.