Exact same problem here. After automatic update to 6.4, WordPress throws a critical error in all pages created with td-composer, accompanied by the following error in apache error.log:
PHP Fatal error: Allowed memory size of 268435456 bytes exhausted (tried to allocate 140617534846248 bytes) in /home/website/public_html/wp-content/plugins/td-composer/includes/shortcodes/vc_single_image.php on line 14'

• This reply was modified 2 years by lstamellos.

I finally located the problem and it was a custom plugin. You can flag this as solved and thank you so much for your time and reply.

I’m going to describe our case for any other Newspaper users out there (or maybe as a nudge to the developers team to establish a more general solution in the theme for some use case scenarios like ours 😉 ) :

Since Newspaper has very limited support for featured videos only from a handful of established video providers (such as YouTube, Vimeo, Facebook and Twitter), we needed to be able to create posts with a featured video from our own PeerTube instance. For this, we used the td_video_support.php as a basis to create a custom plugin with functions that enable editors to add Featured Videos from our own PeerTube instance.

Since td_video_support.php was modified in the 12.3.1 version of Newspaper, we needed to review our custom plugin to include the newly added embed_oembed_html_process_embed_html function.

I expected this would be part of the theme’s documentation so we could do the customization on our own.

Maybe an improvement sometime in the future would be to unify the Featured Video functionality with the core oembed support of WordPress.

Thank you for your time and answer!